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Sample records for structural instability caused

  1. Causes of genome instability

    DEFF Research Database (Denmark)

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

    2015-01-01

    function, chromosome segregation, telomere length). The purpose of this review is to describe the crucial aspects of genome instability, to outline the ways in which environmental chemicals can affect this cancer hallmark and to identify candidate chemicals for further study. The overall aim is to make......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...

  2. 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.

  3. Structural and Material Instability

    DEFF Research Database (Denmark)

    Cifuentes, Gustavo Cifuentes

    This work is a small contribution to the general problem of structural and material instability. In this work, the main subject is the analysis of cracking and failure of structural elements made from quasi-brittle materials like concrete. The analysis is made using the finite element method. Three...

  4. Instabilities and nonequilibrium structures

    International Nuclear Information System (INIS)

    Tirapegui, E.; Villarroel, D.

    1987-01-01

    Physical systems can be studied both near to and far from equilibrium where instabilities appear. The behaviour in these two regions is reviewed in this book, from both the theoretical and application points of view. The influence of noise in these situations is an essential feature which cannot be ignored. It is therefore discussed using phenomenological and theoretical approaches for the numerous problems which still remain in the field. This volume should appeal to mathematicians and physicists interested in the areas of instability, bifurcation theory, dynamical systems, pattern formation, nonequilibrium structures and statistical mechanics. (Auth.)

  5. Delayed chromosomal instability caused by large deletion

    International Nuclear Information System (INIS)

    Ojima, M.; Suzuki, K.; Kodama, S.; Watanabe, M.

    2003-01-01

    Full text: There is accumulating evidence that genomic instability, manifested by the expression of delayed phenotypes, is induced by X-irradiation but not by ultraviolet (UV) light. It is well known that ionizing radiation, such as X-rays, induces DNA double strand breaks, but UV-light mainly causes base damage like pyrimidine dimers and (6-4) photoproducts. Although the mechanism of radiation-induced genomic instability has not been thoroughly explained, it is suggested that DNA double strand breaks contribute the induction of genomic instability. We examined here whether X-ray induced gene deletion at the hprt locus induces delayed instability in chromosome X. SV40-immortalized normal human fibroblasts, GM638, were irradiated with X-rays (3, 6 Gy), and the hprt mutants were isolated in the presence of 6-thioguanine (6-TG). A 2-fold and a 60-fold increase in mutation frequency were found by 3 Gy and 6 Gy irradiation, respectively. The molecular structure of the hprt mutations was determined by multiplex polymerase chain reaction of nine exons. Approximately 60% of 3 Gy mutants lost a part or the entire hprt gene, and the other mutants showed point mutations like spontaneous mutants. All 6 Gy mutants show total gene deletion. The chromosomes of the hprt mutants were analyzed by Whole Human Chromosome X Paint FISH or Xq telomere FISH. None of the point or partial gene deletion mutants showed aberrations of X-chromosome, however total gene deletion mutants induced translocations and dicentrics involving chromosome X. These results suggest that large deletion caused by DNA double strand breaks destabilizes chromosome structure, which may be involved in an induction of radiation-induced genomic instability

  6. Analysis of fluid structural instability in water

    International Nuclear Information System (INIS)

    Piccirillo, N.

    1997-02-01

    Recent flow testing of stainless steel hardware in a high pressure/high temperature water environment produced an apparent fluid-structural instability. The source of instability was investigated by studying textbook theory and by performing NASTRAN finite element analyses. The modal analyses identified the mode that was being excited, but the flutter instability analysis showed that the design is stable if minimal structural damping is present. Therefore, it was suspected that the test hardware was the root cause of the instability. Further testing confirmed this suspicion

  7. 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.

  8. Fanconi anemia: causes and consequences of genetic instability.

    Science.gov (United States)

    Kalb, R; Neveling, K; Nanda, I; Schindler, D; Hoehn, H

    2006-01-01

    Fanconi anemia (FA) is a rare recessive disease that reflects the cellular and phenotypic consequences of genetic instability: growth retardation, congenital malformations, bone marrow failure, high risk of neoplasia, and premature aging. At the cellular level, manifestations of genetic instability include chromosomal breakage, cell cycle disturbance, and increased somatic mutation rates. FA cells are exquisitely sensitive towards oxygen and alkylating drugs such as mitomycin C or diepoxybutane, pointing to a function of FA genes in the defense against reactive oxygen species and other DNA damaging agents. FA is caused by biallelic mutations in at least 12 different genes which appear to function in the maintenance of genomic stability. Eight of the FA proteins form a nuclear core complex with a catalytic function involving ubiquitination of the central FANCD2 protein. The posttranslational modification of FANCD2 promotes its accumulation in nuclear foci, together with known DNA maintenance proteins such as BRCA1, BRCA2, and the RAD51 recombinase. Biallelic mutations in BRCA2 cause a severe FA-like phenotype, as do biallelic mutations in FANCD2. In fact, only leaky or hypomorphic mutations in this central group of FA genes appear to be compatible with life birth and survival. The newly discovered FANCJ (= BRIP1) and FANCM (= Hef ) genes correspond to known DNA-maintenance genes (helicase resp. helicase-associated endonuclease for fork-structured DNA). These genes provide the most convincing evidence to date of a direct involvement of FA genes in DNA repair functions associated with the resolution of DNA crosslinks and stalled replication forks. Even though genetic instability caused by mutational inactivation of the FANC genes has detrimental effects for the majority of FA patients, around 20% of patients appear to benefit from genetic instability since genetic instability also increases the chance of somatic reversion of their constitutional mutations. Intragenic

  9. Loss of centrioles causes chromosomal instability in vertebrate somatic cells.

    Science.gov (United States)

    Sir, Joo-Hee; Pütz, Monika; Daly, Owen; Morrison, Ciaran G; Dunning, Mark; Kilmartin, John V; Gergely, Fanni

    2013-12-09

    Most animal cells contain a centrosome, which comprises a pair of centrioles surrounded by an ordered pericentriolar matrix (PCM). Although the role of this organelle in organizing the mitotic spindle poles is well established, its precise contribution to cell division and cell survival remains a subject of debate. By genetically ablating key components of centriole biogenesis in chicken DT40 B cells, we generated multiple cell lines that lack centrioles. PCM components accumulated in acentriolar microtubule (MT)-organizing centers but failed to adopt a higher-order structure, as shown by three-dimensional structured illumination microscopy. Cells without centrioles exhibited both a delay in bipolar spindle assembly and a high rate of chromosomal instability. Collectively, our results expose a vital role for centrosomes in establishing a mitotic spindle geometry that facilitates correct kinetochore-MT attachments. We propose that centrosomes are essential in organisms in which rapid segregation of a large number of chromosomes needs to be attained with fidelity.

  10. The Economic Causes and Consequences of Social Instability in China

    OpenAIRE

    John Knight

    2012-01-01

    Social instability is a concept that economists rarely analyse, and yet it can lurk behind much economic policy-making. China’s leadership has often publicly expressed its concerns to avoid ‘social instability’. It is viewed as a threat both to the political order and to the continued rapid growth of the economy. This threat to growth in turn endangers the maintenance of social stability. This paper examines the likely economic determinants of social instability, using both surveys and ...

  11. Monoradiculopathy and secondary segmental instability caused by postoperative pars interarticularis fracture: a case report.

    Science.gov (United States)

    Kaner, Tuncay; Tutkan, Ibrahim

    2009-04-01

    Instability can develop after lumbar spinal surgery. What is also known as secondary segmental instability is one of the important causes of failed back syndrome. In this paper, we described a 45-year-old female patient who was diagnosed with secondary segmental instability caused by left L3 pars interarticularis fracture after a high lumbar disc surgery and was subsequently treated with re-operation. We evaluated the clinical course, diagnosis, and treatment methods for secondary segmental instability caused by postoperative pars interarticularis fracture. Furthermore, we emphasized the importance of preserving the pars interarticularis during upper lumbar disc surgeries in order to avoid a potential stress fracture.

  12. Essays on political instability : Measurement, causes and consequences

    NARCIS (Netherlands)

    Jong-A-Pin, R.

    2008-01-01

    In political economy, the concept of political instability plays a prominent role as it raises uncertainty with respect to future institutions and economic policies, thereby affecting the incentives of e.g. households, firms, and politicians. This dissertation contains four quantitative studies on

  13. 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.

  14. Fan-structure wave as a source of earthquake instability

    Science.gov (United States)

    Tarasov, Boris

    2015-04-01

    Today frictional shear resistance along pre-existing faults is considered to be the lower limit on rock shear strength at confined compression corresponding to the seismogenic layer. This determines the lithospheric strength and the primary earthquake mechanism associated with frictional stick-slip instability on pre-existing faults. This paper introduces a recently identified shear rupture mechanism providing a paradoxical feature of hard rocks - the possibility of shear rupture propagation through the highly confined intact rock mass at shear stress levels significantly less than frictional strength. In the new mechanism the rock failure, associated with consecutive creation of small slabs (known as 'domino-blocks') from the intact rock in the rupture tip, is driven by a fan-shaped domino structure representing the rupture head. The fan-head combines such unique features as: extremely low shear resistance (below the frictional strength), self-sustaining stress intensification in the rupture tip (providing easy formation of new domino-blocks), and self-unbalancing conditions in the fan-head (making the failure process inevitably spontaneous and violent). An important feature of the fan-mechanism is the fact that for the initial formation of the fan-structure an enhanced local shear stress is required, however, after completion of the fan-structure it can propagate as a dynamic wave through intact rock mass at shear stresses below the frictional strength. Paradoxically low shear strength of pristine rocks provided by the fan-mechanism determines the lower limit of the lithospheric strength and favours the generation of new faults in pristine rocks in preference to frictional stick-slip instability along pre-existing faults. The new approach reveals an alternative role of pre-existing faults in earthquake activity: they represent local stress concentrates in pristine rock adjoining the fault where special conditions for the fan-mechanism nucleation are created

  15. Charge density wave instabilities and incommensurate structural phase transformations

    International Nuclear Information System (INIS)

    Axe, J.D.

    1977-10-01

    Incommensurate structural phase transformations involve the appearance of modulated atomic displacements with spatial periodicity unrelated to the fundamental periodicity of the basic lattice. In the case of some quasi one- or two-dimensional metals such transformations are the result of Fermi-surface instabilities that also produce electronic charge density waves (CDW's) and soft phonon modes due to metallic electron screening singularities. Incommensurate soft mode instabilities have been found in insulators as well. Recent neutron scattering studies of both the statics and dynamics of incommensurate structural instabilities will be reviewed

  16. Mechanical instability in non-uniform atomic structure: Application to amorphous metal

    International Nuclear Information System (INIS)

    Umeno, Yoshitaka; Kitamura, Takayuki; Tagawa, Motoki

    2007-01-01

    It is important to reveal the deformation of amorphous metal in the atomistic scale level as materials with non-crystal structure have been attracting attention with their prominent functions. In this paper atomistic simulations of tensile deformation of an amorphous model are conducted and local mechanical instability is analyzed to clarify the deformation mechanism of the amorphous structure. Instability causing sharp stress drop is associated with unstable motion of atoms within local region. The size of the region where the unstable atomic motion occurs corresponds to the magnitude of total stress decrease. At instability with large stress decrease the deformation at the onset of the instability propagates to surrounding region, which gives rise to a hysteresis loop in the stress-strain relation. This manifests the microscopic mechanism of the plasticity of amorphous structure

  17. The structure of the Cepheid instability strip

    International Nuclear Information System (INIS)

    Fernie, J.D.

    1990-01-01

    About 100 classical Cepheids having color excesses on a homogeneous system with standard errors of 0.02 or less mag are used with the Feast-Walker period-luminosity-color relation to study the distribution of such stars in the instability strip. It is found that mean (B-V)mag is a better indicator of mean effective temperature than is mean B(i) - mean V(i)(i). The blue edge of the color-magnitude distribution is consistent with the theoretical blue edge for Y = 0.28 and Z = 0.02. Although the highest amplitude stars are found near the center of the period-color array, high- and low-amplitude stars can intermingle, and both kinds are to be found near the edges of the distribution. The same is true on the C-M array. Finally, it is pointed out that the Cepheids do not populate the instability strip uniformly if the red edge is taken to be parallel to the theoretical blue edge. Rather, the local instability region runs as a parallelogram in the C-M array from the theoretical blue edge upward and to the red. 24 refs

  18. An Odontoid Fracture Causing Apnea, Cardiac Instability, and Quadriplegia

    Directory of Open Access Journals (Sweden)

    Christian A. Bowers

    2012-01-01

    Full Text Available Odontoid fractures are typically associated with low rates of acute neurologic deficit and morbidity/mortality in nonelderly patients. In the patient in this case, traumatic injury triggered by a syncopal event led to a combined C1-C2 fracture and a fatal spinal cord injury with apnea, quadriplegia, and cardiovascular instability. We briefly review the anatomical basis for the pathophysiology of cardiac dysfunction following high-cervical spine injury and present an example of a worst-case scenario.

  19. Oxidative DNA damage causes mitochondrial genomic instability in Saccharomyces cerevisiae.

    Science.gov (United States)

    Doudican, Nicole A; Song, Binwei; Shadel, Gerald S; Doetsch, Paul W

    2005-06-01

    Mitochondria contain their own genome, the integrity of which is required for normal cellular energy metabolism. Reactive oxygen species (ROS) produced by normal mitochondrial respiration can damage cellular macromolecules, including mitochondrial DNA (mtDNA), and have been implicated in degenerative diseases, cancer, and aging. We developed strategies to elevate mitochondrial oxidative stress by exposure to antimycin and H(2)O(2) or utilizing mutants lacking mitochondrial superoxide dismutase (sod2Delta). Experiments were conducted with strains compromised in mitochondrial base excision repair (ntg1Delta) and oxidative damage resistance (pif1Delta) in order to delineate the relationship between these pathways. We observed enhanced ROS production, resulting in a direct increase in oxidative mtDNA damage and mutagenesis. Repair-deficient mutants exposed to oxidative stress conditions exhibited profound genomic instability. Elimination of Ntg1p and Pif1p resulted in a synergistic corruption of respiratory competency upon exposure to antimycin and H(2)O(2). Mitochondrial genomic integrity was substantially compromised in ntg1Delta pif1Delta sod2Delta strains, since these cells exhibit a total loss of mtDNA. A stable respiration-defective strain, possessing a normal complement of mtDNA damage resistance pathways, exhibited a complete loss of mtDNA upon exposure to antimycin and H(2)O(2). This loss was preventable by Sod2p overexpression. These results provide direct evidence that oxidative mtDNA damage can be a major contributor to mitochondrial genomic instability and demonstrate cooperation of Ntg1p and Pif1p to resist the introduction of lesions into the mitochondrial genome.

  20. Lateral-Torsional Buckling Instability Caused by Individuals Walking on Wood Composite I-Joists

    Science.gov (United States)

    Villasenor Aguilar, Jose Maria

    Recent research has shown that a significant number of the falls from elevation occur when laborers are working on unfinished structures. Workers walking on wood I-joists on roofs and floors are prone to fall hazards. Wood I-joists have been replacing dimension lumber for many floor systems and a substantial number of roof systems in light-frame construction. Wood I-joists are designed to resist axial stresses on the flanges and shear stresses on the web while minimizing material used. However, wood I-joists have poor resistance to applied lateral and torsional loads and are susceptible to lateral-torsional buckling instability. Workers walking on unbraced or partially braced wood I-joists can induce axial and lateral forces as well as twist. Experimental testing demonstrated that workers cause lateral-torsional buckling instability in wood I-joists. However, no research was found related to the lateral-torsional buckling instability induced by individuals walking on the wood I-joists. Furthermore, no research was found considering the effects of the supported end conditions and partial bracing in the lateral-torsional buckling instability of wood I-joists. The goal of this research was to derive mathematical models to predict the dynamic lateral-torsional buckling instability of wood composite I-joists loaded by individuals walking considering different supported end conditions and bracing system configurations. The dynamic lateral-torsional buckling instability was analyzed by linearly combining the static lateral-torsional buckling instability with the lateral bending motion of the wood Ijoists. Mathematical models were derived to calculate the static critical loads for the simply supported end condition and four wood I-joist hanger supported end conditions. Additionally, mathematical models were derived to calculate the dynamic maximum lateral displacements and positions of the individual walking on the wood Ijoists for the same five different supported end

  1. Instability of a vehicle moving on an elastic structure

    NARCIS (Netherlands)

    Veritchev, S.N.

    2002-01-01

    Vibrations of a vehicle that moves on a long elastic structure can become unstable because of elastic waves that the vehicle generates in the structure. A typical example of the vehicle that can experience such instability is a high-speed train. Moving with a sufficiently high speed, this train

  2. Radial mode structure of curvature-driven instabilities in EBT

    International Nuclear Information System (INIS)

    Spong, D.A.

    1983-01-01

    Viewgraphs describe the theoretical treatment of the radial mode structure of plasma instabilities in the Elmo Bumpy Torus. The calculation retains nonlocal structure of the modes, connects inner and outer ring regions together, uses a self-consistent finite β, includes the relativistic effects for the hot electron ring, and examines a wide range of parameters

  3. Community Structural Instability, Anomie, Imitation and Adolescent Suicidal Behavior

    Science.gov (United States)

    Thorlindsson, Thorolfur; Bernburg, Jon Gunnar

    2009-01-01

    The current study examines the contextual effects of community structural characteristics, as well as the mediating role of key social mechanisms, on youth suicidal behavior in Iceland. We argue that the contextual influence of community structural instability on youth suicidal behavior should be mediated by weak attachment to social norms and…

  4. Current filamentation caused by the electrochemical instability in a fully ionized plasma

    International Nuclear Information System (INIS)

    Haines, M.G.; Marsh, F.

    1983-01-01

    This chapter is primarily concerned with the non-linear development of electrothermal instabilities in a fully ionized plasma discharge in which the current is predominantly carried parallel to an applied magnetic field, as in the Tokamak configuration. Discusses instabilities with wave-number K perpendicular to magnetic field B and current J; the non-linear steady state; amplitude of the filaments; and runaway electrons and ion acoustic instabilities. Concludes that the steady non-linear amplitude of the fully developed instability shows a spiky filamentary structure with the possibility of the generation of runaway electrons and ion acoustic turbulence in the current maxima. Finds that the addition of bremsstrahlung radiation loss enhances the instability, reducing the critical ratio of T /SUB e/ to T /SUB i/ for its onset, and yielding a maximum ion temperature attainable by Joule heating and equipartition

  5. Molecular causes and consequences of genetic instability with respect to the FA/BRCA Caretaker Pathway

    OpenAIRE

    Neveling, Kornelia

    2012-01-01

    In the context of this thesis, I investigated the molecular causes and functional consequences of genetic instability using a human inherited disease, Fanconi anemia. FA patients display a highly variable clinical phenotype, including congenital abnormalities, progressive bone marrow failure and a high cancer risk. The FA cellular phenotype is characterized by spontaneous and inducible chromosomal instability, and a typical S/G2 phase arrest after exposure to DNA-damaging agents. So far, 13 g...

  6. Effect of magnetic field on ablatively driven Richtmyer-Meshkov instability induced by interfacial nonlinear structure

    International Nuclear Information System (INIS)

    Labakanta Mandal; Banerjee, R.; Roy, S.; Khan, M.; Gupta, M.R.

    2010-01-01

    Complete text of publication follows. In an Inertial Confinement Fusion (ICF) situation, laser driven ablation front of an imploding capsule is subjected to the fluid instabilities like Rayleigh-Taylor (RT), Richtmyer-Meshkov (RM) and Kelvin-Helmholtz (KH) instability. In this case dense core is compressed and accelerated by low density ablating plasma. During this process laser driven shocks interact the interface and hence it becomes unstable due to the formation of nonlinear structure like bubble and spike. The nonlinear structure is called bubble if the lighter fluid pushes inside the heavier fluid and spike, if opposite takes place. R-M instability causes non-uniform compression of ICF fuel pellets and needs to be mitigated. Scientists and researchers are much more interested on RM instability both from theoretical and experimental points of view. In this article, we have presented the analytical expression for the growth rate and velocity for the nonlinear structures due to the effect of magnetic field of fluid using potential flow model. The magnetic field is assumed to be parallel to the plane of two fluid interfaces. If the magnetic field is restricted only to either side of interface the R-M instability can be stabilized or destabilized depending on whether the magnetic pressure on the interface opposes the instability driving shock pressure or acts in the same direction. An interesting result is that if both the fluids are magnetized, interface as well as velocity of bubble and spike will show oscillating stabilization and R-M instability is mitigated. All analytical results are also supported by numerical results. Numerically it is seen that magnetic field above certain minimum value reduces the instability for compression the target in ICF.

  7. Kelvin-Helmholtz instability as a possible cause of edge localized modes

    International Nuclear Information System (INIS)

    Strauss, H.R.

    1992-01-01

    Edge localized modes may be a Kelvin-Helmholtz instability caused by the sheared rotation of H-mode plasmas. The Kelvin-Helmholtz instability is stabilized by coupling to Alfven waves. There is a critical velocity gradient, of the order of the Alfven velocity divided by the magnetic shear length. This is verified in a numerical simulation. The critical velocity shear is consistent with experiment. A non-linear simulation shows how the Kelvin-Helmholtz mode can cause oscillations of the velocity profile. (author). Letter-to-the-editor. 13 refs, 6 figs

  8. Slope instability caused by small variations in hydraulic conductivity

    Science.gov (United States)

    Reid, M.E.

    1997-01-01

    Variations in hydraulic conductivity can greatly modify hillslope ground-water flow fields, effective-stress fields, and slope stability. In materials with uniform texture, hydraulic conductivities can vary over one to two orders of magnitude, yet small variations can be difficult to determine. The destabilizing effects caused by small (one order of magnitude or less) hydraulic conductivity variations using ground-water flow modeling, finite-element deformation analysis, and limit-equilibrium analysis are examined here. Low hydraulic conductivity materials that impede downslope ground-water flow can create unstable areas with locally elevated pore-water pressures. The destabilizing effects of small hydraulic heterogeneities can be as great as those induced by typical variations in the frictional strength (approximately 4??-8??) of texturally similar materials. Common "worst-case" assumptions about ground-water flow, such as a completely saturated "hydrostatic" pore-pressure distribution, do not account for locally elevated pore-water pressures and may not provide a conservative slope stability analysis. In site characterization, special attention should be paid to any materials that might impede downslope ground-water flow and create unstable regions.

  9. Causes of Marital Instability in the Port-Harcourt Municipality, Nigeria

    African Journals Online (AJOL)

    Causes of Marital Instability in the Port-Harcourt Municipality, Nigeria: ... clusters of five, viz; absence of love and trust, anti-social vices, economic, socio-cultural and ... are the most positive indicators to marriage stability in our Nigerian homes.

  10. Experimental investigation of bubble plume structure instability

    Energy Technology Data Exchange (ETDEWEB)

    Marco Simiano; Robert Zboray; Francois de Cachard [Thermal-Hydraulics Laboratory, Paul Scherrer Institut, 5232 Villigen PSI (Switzerland); Djamel Lakehal; George Yadigaroglu [Institute of Energy Technology, Swiss Federal Institute of Technology, ETH-Zentrum/CLT, 8092 Zurich (Switzerland)

    2005-07-01

    Full text of publication follows: The hydrodynamic properties of a 3D bubble plume in a large water pool are investigated experimentally. Bubble plumes are present in various industrial processes, including chemical plants, stirred reactors, and nuclear power plants, e.g. in BWR suppression pools. In these applications, the main issue is to predict the currents induced by the bubbles in the liquid phase, and to determine the consequent mixing. Bubble plumes, especially large and unconfined ones, present strong 3D effects and a superposition of different characteristic length scales. Thus, they represent relevant test cases for assessment and verification of 3D models in thermal-hydraulic codes. Bubble plumes are often unsteady, with fluctuations in size and shape of the bubble swarm, and global movements of the plume. In this case, local time-averaged data are not sufficient to characterize the flow. Additional information regarding changes in plume shape and position is required. The effect of scale on the 3D flow structure and stability being complex, there was a need to conduct studies in a fairly large facility, closer to industrial applications. Air bubble plumes, up to 30 cm in base diameter and 2 m in height were extensively studied in a 2 m diameter water pool. Homogeneously sized bubbles were obtained using a particular injector. The main hydrodynamic parameters. i.e., gas and liquid velocities, void fraction, bubble shape and size, plume shape and position, were determined experimentally. Photographic and image processing techniques were used to characterize the bubble shape, and double-tip optical probes to measure bubble size and void fraction. Electromagnetic probes measured the recirculation velocity in the pool. Simultaneous two-phase flow particle image velocimetry (STPFPIV) in a vertical plane containing the vessel axis provided instantaneous velocity fields for both phases and therefore the relative velocity field. Video recording using two CCD

  11. Rayleigh-Taylor instability in multi-structured spherical targets

    International Nuclear Information System (INIS)

    Gupta, N.K.; Lawande, S.V.

    1986-01-01

    An eigenvalue equation for the exponential growth rate of the Rayleigh-Taylor instability is derived in spherical geometry. The free surface and jump boundary conditions are obtained from the eigenvalue equation. The eigenvalue equation is solved in the cases where the initial fluid density profile has a step function or exponential variation in space and analytical formulae for growth rate of the instability are obtained. The solutions for the step function are generalized for any number N of spherical zones forming an arbitrary fluid density profile. The results of the numerical calculations for N spherical zones are compared with the exact analytical results for exponential fluid density profile with N=10 and a good agreement is observed. The formalism is further used to study the effects of density gradients on Rayleigh-Taylor instability in spherical geometry. Also analytical formulae are presented for a particular case of N=3 and shell targets. The formalism developed here can be used to study the growth of the instability in present day multi-structured shell targets. (author)

  12. Electron heating caused by the ion-acoustic decay instability in a finite-length system

    International Nuclear Information System (INIS)

    Rambo, P.W.; Woo, W.; DeGroot, J.S.; Mizuno, K.

    1984-01-01

    The ion-acoustic decay instability is investigated for a finite-length plasma with density somewhat below the cutoff density of the electromagnetic driver (napprox.0.7n/sub c/). For this regime, the heating in a very long system can overpopulate the electron tail and cause linear saturation of the low phase velocity electron plasma waves. For a short system, the instability is nonlinearly saturated at larger amplitude by ion trapping. Absorption can be significantly increased by the large-amplitude ion waves. These results compare favorably with microwave experiments

  13. The effect of internal magnetic structure on the fishbone instability

    International Nuclear Information System (INIS)

    Roberts, D.W.; Powell, E.; Kaita, R.; Bell, R.; Chance, M.; Hatcher, R.; Holland, A.; Kaye, S.; Kessel, C.; Kugel, H.; LeBlanc, B.; Manickam, J.; Okabayashi, M.; Paul, S.; Pomphrey, N.; Sauthoff, N.; Sesnic, S.; Takahashi, H.; White, R.; Asakura, N.; Duperrex, P.; Gammel, G.

    1992-01-01

    Plasmas exhibiting the ''fishbone'' instability studied on the PBX-M tokamak show a distinct relationship between the plasma shape, the internal magnetic structure, and the presence or absence of fast ion losses associated with the fishbone mode. We have, for the first time, carried out measurements of the magnetic safety factor profile in fishbone-unstable plasmas, and used the knowledge of the associated experimental equilibria to compare the stability and fast ion loss properties of these plasmas with experimental observations

  14. Fast Transverse Beam Instability Caused by Electron Cloud Trapped in Combined Function Magnets

    Energy Technology Data Exchange (ETDEWEB)

    Antipov, Sergey [Univ. of Chicago, IL (United States)

    2017-03-01

    Electron cloud instabilities affect the performance of many circular high-intensity particle accelerators. They usually have a fast growth rate and might lead to an increase of the transverse emittance and beam loss. A peculiar example of such an instability is observed in the Fermilab Recycler proton storage ring. Although this instability might pose a challenge for future intensity upgrades, its nature had not been completely understood. The phenomena has been studied experimentally by comparing the dynamics of stable and unstable beam, numerically by simulating the build-up of the electron cloud and its interaction with the beam, and analytically by constructing a model of an electron cloud driven instability with the electrons trapped in combined function dipoles. Stabilization of the beam by a clearing bunch reveals that the instability is caused by the electron cloud, trapped in beam optics magnets. Measurements of microwave propagation confirm the presence of the cloud in the combined function dipoles. Numerical simulations show that up to 10$^{-2}$ of the particles can be trapped by their magnetic field. Since the process of electron cloud build-up is exponential, once trapped this amount of electrons significantly increases the density of the cloud on the next revolution. In a combined function dipole this multi-turn accumulation allows the electron cloud reaching final intensities orders of magnitude greater than in a pure dipole. The estimated fast instability growth rate of about 30 revolutions and low mode frequency of 0.4 MHz are consistent with experimental observations and agree with the simulations. The created instability model allows investigating the beam stability for the future intensity upgrades.

  15. Macroeconomic instability: its causes and consequences for the economy of Ukraine

    Directory of Open Access Journals (Sweden)

    Natalia SKOROBOGATOVA

    2016-06-01

    Full Text Available The article deals with the concepts of appearance and elimination of macroeconomic instability, and the Keynesian approach for overcoming issues in Ukraine’s macroeconomic instability. Based on the Ukraine Statistics Service and World Bank data, Ukraine's economy tendencies have been defined: the country has not reached the pre-crisis economic level. The article identifies the reasons of negative balance payments and budget deficit: a decrease in production value, negative trade balance, growth of foreign creditor’s debt, currency instability, an increase in budget spending. The dynamics of income and expenditure within Ukraine budget has been analyzed, and also the destructiveness of existing approaches for the main financial documents has been grounded. Considering Ukraine’s economic and political situation, the main causes of macroeconomic instability are systematized. Government-implemented approaches for overcoming the macroeconomic instability have been suggested. The article introduces an approach for minimizing the negative effects on businesses, based on the timely identification of macroeconomic risks in terms of internal and external management. The possible negative impacts in case the timely decisions are not implemented have been assessed.

  16. Evaluation of bridge instability caused by dynamic scour based on fractal theory

    International Nuclear Information System (INIS)

    Lin, Tzu-Kang; Shian Chang, Yu; Wu, Rih-Teng; Chang, Kuo-Chun

    2013-01-01

    Given their special structural characteristics, bridges are prone to suffer from the effects of many hazards, such as earthquakes, wind, or floods. As most of the recent unexpected damage and destruction of bridges has been caused by hydraulic issues, monitoring the scour depth of bridges has become an important topic. Currently, approaches to scour monitoring mainly focus on either installing sensors on the substructure of a bridge or identifying the physical parameters of a bridge, which commonly face problems of system survival or reliability. To solve those bottlenecks, a novel structural health monitoring (SHM) concept was proposed by utilizing the two dominant parameters of fractal theory, including the fractal dimension and the topothesy, to evaluate the instability condition of a bridge structure rapidly. To demonstrate the performance of this method, a series of experiments has been carried out. The function of the two parameters was first determined using data collected from a single bridge column scour test. As the fractal dimension gradually decreased, following the trend of the scour depth, it was treated as an alternative to the fundamental frequency of a bridge structure in the existing methods. Meanwhile, the potential of a positive correlation between the topothesy and the amplitude of vibration data was also investigated. The excellent sensitivity of the fractal parameters related to the scour depth was then demonstrated in a full-bridge experiment. Moreover, with the combination of these two parameters, a safety index to detect the critical scour condition was proposed. The experimental results have demonstrated that the critical scour condition can be predicted by the proposed safety index. The monitoring system developed greatly advances the field of bridge scour health monitoring and offers an alternative choice to traditional scour monitoring technology. (paper)

  17. Sudden onset odontoid fracture caused by cervical instability in hypotonic cerebral palsy.

    Science.gov (United States)

    Shiohama, Tadashi; Fujii, Katsunori; Kitazawa, Katsuhiko; Takahashi, Akiko; Maemoto, Tatsuo; Honda, Akihito

    2013-11-01

    Fractures of the upper cervical spine rarely occur but carry a high rate of mortality and neurological disabilities in children. Although odontoid fractures are commonly caused by high-impact injuries, cerebral palsy children with cervical instability have a risk of developing spinal fractures even from mild trauma. We herein present the first case of an odontoid fracture in a 4-year-old boy with cerebral palsy. He exhibited prominent cervical instability due to hypotonic cerebral palsy from infancy. He suddenly developed acute respiratory failure, which subsequently required mechanical ventilation. Neuroimaging clearly revealed a type-III odontoid fracture accompanied by anterior displacement with compression of the cervical spinal cord. Bone mineral density was prominently decreased probably due to his long-term bedridden status and poor nutritional condition. We subsequently performed posterior internal fixation surgically using an onlay bone graft, resulting in a dramatic improvement in his respiratory failure. To our knowledge, this is the first report of an odontoid fracture caused by cervical instability in hypotonic cerebral palsy. Since cervical instability and decreased bone mineral density are frequently associated with cerebral palsy, odontoid fractures should be cautiously examined in cases of sudden onset respiratory failure and aggravated weakness, especially in hypotonic cerebral palsy patients. Copyright © 2012 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

  18. Primary postural instability: a cause of recurrent sudden falls in the elderly.

    Science.gov (United States)

    Djaldetti, R; Lorberboym, M; Melamed, E

    2006-12-01

    Elderly patients with recurrent falls are frequently diagnosed with an extrapyramidal syndrome. This study aims to characterise a distinct group of patients with recurrent falls and postural instability as a hallmark of the clinical examination. The study took place in the Movement Disorders Unit, Rabin Medical Center, Petah Tiqva, Israel among 26 patients with recurrent falls who had no clinical evidence of a neurodegenerative disease. Medical records, neurological examination and brain imaging studies were assessed. Falls in these patients were sudden, unprovoked, with no vertigo or loss of consciousness. All had postural instability with minimal or no abnormality on the neurological examination. Brain imaging showed diffuse ischaemic changes in 65%. [(123)I]-FPCIT SPECT with the dopamine transporter ligand, performed in five patients, was normal in all. Recurrent falls might be caused by a neurological syndrome that primarily affects balance control. The importance of identifying this disorder is its distinction from other parkinsonian syndromes causing falls.

  19. Odontoid pannus formation in a patient with ankylosing spondylitis causing atlanto-axial instability

    Science.gov (United States)

    Rajak, Rizwan; Wardle, Phil; Rhys-Dillon, Ceril; Martin, James C

    2012-01-01

    Ankylosing spondylitis is one of the commonest inflammatory diseases of the axial skeleton and can be complicated by atlanto-axial instability. This serious and likely underestimated complication can be easily overlooked. However, there are clear features which can help alert suspicion to initiate the appropriate investigations with imaging that is very effective at diagnosing and assessing this complication. The authors report an unusual case where odontoid pannus formation, akin to that seen in rheumatoid arthritis, was the underlying cause. PMID:22665557

  20. Analysis of the Instability Phenomena Caused by Steam in High-Pressure Turbines

    Directory of Open Access Journals (Sweden)

    Paolo Pennacchi

    2011-01-01

    Full Text Available Instability phenomena in steam turbines may happen as a consequence of certain characteristics of the steam flow as well as of the mechanical and geometrical properties of the seals. This phenomenon can be modeled and the raise of the steam flow and pressure causes the increase of the cross coupled coefficients used to model the seal stiffness. As a consequence, the eigenvalues and eigenmodes of the mathematical model of the machine change. The real part of the eigenvalue associated with the first flexural normal mode of the turbine shaft may become positive causing the conditions for unstable vibrations. The original contribution of the paper is the application of a model-based analysis of the dynamic behavior of a large power unit, affected by steam-whirl instability phenomena. The model proposed by the authors allows studying successfully the experimental case. The threshold level of the steam flow that causes instability conditions is analyzed and used to define the stability margin of the power unit.

  1. X-band microwave generation caused by plasma-sheath instability

    International Nuclear Information System (INIS)

    Bliokh, Y.; Felsteiner, J.; Slutsker, Ya. Z.

    2012-01-01

    It is well known that oscillations at the electron plasma frequency may appear due to instability of the plasma sheath near a positively biased electrode immersed in plasma. This instability is caused by transit-time effects when electrons, collected by this electrode, pass through the sheath. Such oscillations appear as low-power short spikes due to additional ionization of a neutral gas in the electrode vicinity. Herein we present first results obtained when the additional ionization was eliminated. We succeeded in prolonging the oscillations during the whole time a positive bias was applied to the electrode. These oscillations could be obtained at much higher frequency than previously reported (tens of GHz compared to few hundreds of MHz) and power of tens of mW. These results in combination with presented theoretical estimations may be useful, e.g., for plasma diagnostics.

  2. A mutation in the centriole-associated protein centrin causes genomic instability via increased chromosome loss in Chlamydomonas reinhardtii

    Directory of Open Access Journals (Sweden)

    Marshall Wallace F

    2005-05-01

    Full Text Available Abstract Background The role of centrioles in mitotic spindle function remains unclear. One approach to investigate mitotic centriole function is to ask whether mutation of centriole-associated proteins can cause genomic instability. Results We addressed the role of the centriole-associated EF-hand protein centrin in genomic stability using a Chlamydomonas reinhardtii centrin mutant that forms acentriolar bipolar spindles and lacks the centrin-based rhizoplast structures that join centrioles to the nucleus. Using a genetic assay for loss of heterozygosity, we found that this centrin mutant showed increased genomic instability compared to wild-type cells, and we determined that the increase in genomic instability was due to a 100-fold increase in chromosome loss rates compared to wild type. Live cell imaging reveals an increased rate in cell death during G1 in haploid cells that is consistent with an elevated rate of chromosome loss, and analysis of cell death versus centriole copy number argues against a role for multipolar spindles in this process. Conclusion The increased chromosome loss rates observed in a centrin mutant that forms acentriolar spindles suggests a role for centrin protein, and possibly centrioles, in mitotic fidelity.

  3. Mathematical models for suspension bridges nonlinear structural instability

    CERN Document Server

    Gazzola, Filippo

    2015-01-01

    This work provides a detailed and up-to-the-minute survey of the various stability problems that can affect suspension bridges. In order to deduce some experimental data and rules on the behavior of suspension bridges, a number of historical events are first described, in the course of which several questions concerning their stability naturally arise. The book then surveys conventional mathematical models for suspension bridges and suggests new nonlinear alternatives, which can potentially supply answers to some stability questions. New explanations are also provided, based on the nonlinear structural behavior of bridges. All the models and responses presented in the book employ the theory of differential equations and dynamical systems in the broader sense, demonstrating that methods from nonlinear analysis can allow us to determine the thresholds of instability.

  4. Minor or occult ankle instability as a cause of anterolateral pain after ankle sprain.

    Science.gov (United States)

    Vega, Jordi; Peña, Fernando; Golanó, Pau

    2016-04-01

    The aim of this study was to determine which intra-articular injuries are associated with chronic anterolateral pain and functional instability after an ankle sprain. From 2008 to 2010, records of all patients who underwent ankle joint arthroscopy with anterolateral pain and functional instability after an ankle sprain were reviewed. A systematic arthroscopic examination of the intra-articular structures of the ankle joint was performed. Location and characteristics of the injuries were identified and recorded. A total of 36 ankle arthroscopic procedures were reviewed. A soft-tissue occupying mass over the lateral recess was present in 18 patients (50%). A partial injury of the anterior talofibular ligament (ATFL) was observed in 24 patients (66.6%). Cartilage abrasion due to the distal fascicle of the anteroinferior tibiofibular ligament coming into contact with the talus was seen in 21 patients (58.3%), but no thickening of the ligament was observed. Injury to the intra-articular posterior structures, including the transverse ligament in 19 patients (52.7%) and the posterior surface of the distal tibia in 21 patients (58.3%), was observed. Intra-articular pathological findings have been observed in patients affected by anterolateral pain after an ankle sprain. Despite no demonstrable abnormal lateral laxity, morphologic ATFL abnormality has been observed on arthroscopic evaluation. An injury of the ATFL is present in patients with chronic anterolateral pain and functional instability after an ankle sprain. A degree of microinstability due to a deficiency of the ATFL could explain the intra-articular pathological findings and the patients' complaints. IV.

  5. The Internal Causes of Political Instability in the Republic of Turkey

    Directory of Open Access Journals (Sweden)

    Sergey Borisovich Druzhilovsky

    2016-01-01

    Full Text Available The article examines the causes of the permanent political instability in the Turkish Republic, which leads to frequent change of governments, degradation of political parties and changing of policies. On the example of the activities of different cabinets it is showen that the basis of their instability is the frequent creation of coalition governments consisting of parties that stand on different ideological positions. Inter-party antagonism, in its turn, is a consequence of the split of the Turkish society along civilizational, ethnic and religious grounds, which determines the different political orientation of the various layers of the Turkish society. At the same time the article shows the examples of the undoubted efficiency of one-party governments, however they never get support from the opposition parties, and eventually also fail to effectively and consistently implement their proposed policies. The author also deals with a policy of the ruling today in Turkey, the Islamist Party of Justice and Development, which after several years of successful political and economic reforms to date entered the period of deep crisis and is increasingly losing its authority and influence both in Turkey and in neighboring countries.

  6. Carbody elastic vibrations of high-speed vehicles caused by bogie hunting instability

    Science.gov (United States)

    Wei, Lai; Zeng, Jing; Chi, Maoru; Wang, Jianbin

    2017-09-01

    In particular locations of the high-speed track, the worn wheel profile matched up with the worn rail profile will lead to an extremely high-conicity wheel-rail contact. Consequently, the bogie hunting instability arises, which further results in the so-called carbody shaking phenomenon. In this paper, the carbody elastic vibrations of a high-speed vehicle in service are firstly introduced. Modal tests are conducted to identity the elastic modes of the carbody. The ride comfort and running safety indices for the tested vehicle are evaluated. The rigid-flexible coupling dynamic model for the high-speed passenger car is then developed by using the FE and MBS coupling approach. The rail profiles in those particular locations are measured and further integrated into the simulation model to reproduce the bogie hunting and carbody elastic vibrations. The effects of wheel and rail wear on the vehicle system response, e.g. wheelset bifurcation graph and carbody vibrations, are studied. Two improvement measures, including the wheel profile modification and rail grinding, are proposed to provide possible solutions. It is found that the wheel-rail contact conicity can be lowered by decreasing wheel flange thickness or grinding rail corner, which is expected to improve the bogie hunting stability under worn rail and worn wheel conditions. The carbody elastic vibrations caused by bogie hunting instability can be further restrained.

  7. Buckling Instability Causes Inertial Thrust for Spherical Swimmers at All Scales

    Science.gov (United States)

    Djellouli, Adel; Marmottant, Philippe; Djeridi, Henda; Quilliet, Catherine; Coupier, Gwennou

    2017-12-01

    Microswimmers, and among them aspirant microrobots, generally have to cope with flows where viscous forces are dominant, characterized by a low Reynolds number (Re). This implies constraints on the possible sequences of body motion, which have to be nonreciprocal. Furthermore, the presence of a strong drag limits the range of resulting velocities. Here, we propose a swimming mechanism which uses the buckling instability triggered by pressure waves to propel a spherical, hollow shell. With a macroscopic experimental model, we show that a net displacement is produced at all Re regimes. An optimal displacement caused by nontrivial history effects is reached at intermediate Re. We show that, due to the fast activation induced by the instability, this regime is reachable by microscopic shells. The rapid dynamics would also allow high-frequency excitation with standard traveling ultrasonic waves. Scale considerations predict a swimming velocity of order 1 cm /s for a remote-controlled microrobot, a suitable value for biological applications such as drug delivery.

  8. PTEN C-Terminal Deletion Causes Genomic Instability and Tumor Development

    Directory of Open Access Journals (Sweden)

    Zhuo Sun

    2014-03-01

    Full Text Available Tumor suppressor PTEN controls genomic stability and inhibits tumorigenesis. The N-terminal phosphatase domain of PTEN antagonizes the PI3K/AKT pathway, but its C-terminal function is less defined. Here, we describe a knockin mouse model of a nonsense mutation that results in the deletion of the entire Pten C-terminal region, referred to as PtenΔC. Mice heterozygous for PtenΔC develop multiple spontaneous tumors, including cancers and B cell lymphoma. Heterozygous deletion of the Pten C-terminal domain also causes genomic instability and common fragile site rearrangement. We found that Pten C-terminal disruption induces p53 and its downstream targets. Simultaneous depletion of p53 promotes metastasis without influencing the initiation of tumors, suggesting that p53 mainly suppresses tumor progression. Our data highlight the essential role of the PTEN C terminus in the maintenance of genomic stability and suppression of tumorigenesis.

  9. Human RTEL1 deficiency causes Hoyeraal-Hreidarsson syndrome with short telomeres and genome instability.

    Science.gov (United States)

    Le Guen, Tangui; Jullien, Laurent; Touzot, Fabien; Schertzer, Michael; Gaillard, Laetitia; Perderiset, Mylène; Carpentier, Wassila; Nitschke, Patrick; Picard, Capucine; Couillault, Gérard; Soulier, Jean; Fischer, Alain; Callebaut, Isabelle; Jabado, Nada; Londono-Vallejo, Arturo; de Villartay, Jean-Pierre; Revy, Patrick

    2013-08-15

    Hoyeraal-Hreidarsson syndrome (HHS), a severe variant of dyskeratosis congenita (DC), is characterized by early onset bone marrow failure, immunodeficiency and developmental defects. Several factors involved in telomere length maintenance and/or protection are defective in HHS/DC, underlining the relationship between telomere dysfunction and these diseases. By combining whole-genome linkage analysis and exome sequencing, we identified compound heterozygous RTEL1 (regulator of telomere elongation helicase 1) mutations in three patients with HHS from two unrelated families. RTEL1 is a DNA helicase that participates in DNA replication, DNA repair and telomere integrity. We show that, in addition to short telomeres, RTEL1-deficient cells from patients exhibit hallmarks of genome instability, including spontaneous DNA damage, anaphase bridges and telomeric aberrations. Collectively, these results identify RTEL1 as a novel HHS-causing gene and highlight its role as a genomic caretaker in humans.

  10. Nonlinear evolution of single spike structure and vortex in Richtmeyer-Meshkov instability

    International Nuclear Information System (INIS)

    Fukuda, Yuko O.; Nishihara, Katsunobu; Okamoto, Masayo; Nagatomo, Hideo; Matsuoka, Chihiro; Ishizaki, Ryuichi; Sakagami, Hitoshi

    1999-01-01

    Nonlinear evolution of single spike structure and vortex in the Richtmyer-Meshkov instability is investigated for two dimensional case, and axial symmetric and non axial symmetric cases with the use of a three-dimensional hydrodynamic code. It is shown that singularity appears in the vorticity left by transmitted and reflected shocks at a corrugated interface. This singularity results in opposite sign of vorticity along the interface that causes double spiral structure of the spike. Difference of nonlinear growth rate and double spiral structure among three cases is also discussed by visualization of simulation data. In a case that there is no slip-off of initial spike axis, vorticity ring is relatively stable, but phase rotation occurs. (author)

  11. Weak oceanic heat transport as a cause of the instability of glacial climates

    Energy Technology Data Exchange (ETDEWEB)

    Colin de Verdiere, Alain [Universite de Bretagne Occidentale, Laboratoire de Physique des Oceans, Alain Colin de Verdiere, Brest 3 (France); Te Raa, L. [Utrecht University, Institute for Marine and Atmospheric Research Utrecht, Utrecht (Netherlands); Netherlands Organisation for Applied Scientific Research TNO, The Hague (Netherlands)

    2010-12-15

    The stability of the thermohaline circulation of modern and glacial climates is compared with the help of a two dimensional ocean - atmosphere - sea ice coupled model. It turns out to be more unstable as less freshwater forcing is required to induce a polar halocline catastrophy in glacial climates. The large insulation of the ocean by the extensive sea ice cover changes the temperature boundary condition and the deepwater formation regions moves much further South. The nature of the instability is of oceanic origin, identical to that found in ocean models under mixed boundary conditions. With similar strengths of the oceanic circulation and rates of deep water formation for warm and cold climates, the loss of stability of the cold climate is due to the weak thermal stratification caused by the cooling of surface waters, the deep water temperatures being regulated by the temperature of freezing. Weaker stratification with similar overturning leads to a weakening of the meridional oceanic heat transport which is the major negative feedback stabilizing the oceanic circulation. Within the unstable regime periodic millennial oscillations occur spontaneously. The climate oscillates between a strong convective thermally driven oceanic state and a weak one driven by large salinity gradients. Both states are unstable. The atmosphere of low thermal inertia is carried along by the oceanic overturning while the variation of sea ice is out of phase with the oceanic heat content. During the abrupt warming events that punctuate the course of a millennial oscillation, sea ice variations are shown respectively to damp (amplify) the amplitude of the oceanic (atmospheric) response. This sensitivity of the oceanic circulation to a reduced concentration of greenhouse gases and to freshwater forcing adds support to the hypothesis that the millennial oscillations of the last glacial period, the so called Dansgaard - Oeschger events, may be internal instabilities of the climate system

  12. "Sausage-string" appearance of arteries and arterioles can be caused by an instability of the blood vessel wall

    DEFF Research Database (Denmark)

    Jacobsen, Jens Christian Brings; Beierholm, Ulrik; Mikkelsen, Rene

    2002-01-01

    Vascular damage induced by acute hypertension is preceded by a peculiar pattern where blood vessels show alternating regions of constrictions and dilations ("sausages on a string"). The pattern occurs in the smaller blood vessels, and it plays a central role in causing the vascular damage. A rela...... phenomenon. Experimental data suggest that the structural changes induced by the instability may cause secondary damage to the wall of small arteries and arterioles in the form of endothelial hyperpermeability followed by local fibrinoid necrosis of the vascular wall.......Vascular damage induced by acute hypertension is preceded by a peculiar pattern where blood vessels show alternating regions of constrictions and dilations ("sausages on a string"). The pattern occurs in the smaller blood vessels, and it plays a central role in causing the vascular damage....... A related vascular pattern has been observed in larger vessels from several organs during angiography. In the larger vessels the occurrence of the pattern does not appear to be related to acute hypertension. A unifying feature between the phenomenon in large and small vessels seems to be an increase...

  13. Experimental investigation of tearing-instability phenomena for structural materials

    International Nuclear Information System (INIS)

    Vassilaros, M.G.; Gudas, J.P.; Joyce, J.A.

    1982-04-01

    Objective was to extend the range of tearing instability validation experiments utilizing the compact specimen to include high toughness alloys. J-Integral tests of ASTM A106; ASTM A516, Grade 70; ASTM A533B; HY-80; and HY-130 steels were performed in a variably compliant screw-driven test machine. Results were analyzed with respect to the materials J/sub I/-R curves and various models of T/sub applied/ for the compact specimen. Tearing instability theory was validated for these high toughness materials. For the cases of highly curved J/sub I/-R curves, it was shown that the actual value of T/sub material/ at the point of instability should be employed rather than the average of T/sub material/ value. The T/sub applied/ analysis of Paris and coworkers applied to the compact specimen appears to be nonconservative in predicting the point of instability; whereas, the T/sub applied/ analysis of Ernst and coworkers appears to be accurate, but requires precision beyond that displayed in this program. The generalized Paris analysis applied to the compact specimen and evaluated at maximum load was most consistent in predicting instability. 16 figures, 3 tables

  14. Experimental investigation of tearing-instability phenomena for structural materials

    International Nuclear Information System (INIS)

    Vassilaros, M.G.; Gudas, J.P.; Joyce, J.A.

    1982-08-01

    The objective of this investigation was to extend the range of tearing-instability validation experiments utilizing the compact specimen to include high-toughness alloys. J-Integral tests of ASTM A106; ASTM A516, Grade 70; ASTM A533B; HY-80; and HY-130 steels were performed in a variably compliant screw-driven test machine. Results were analyzed with respect to the materials J/sub I/-R curves and various models of T/sub applied/ for the compact specimen. Tearing instability theory was validated for these high-toughess materials. For the cases of highly curved J/sub I/-R curves, it was shown that the actual value of T/sub material/ at the point of instability should be employed rather than the average T/sub material/ value. The T/sub applied/ analysis of Paris and coworkers applied to the compact specimen appears to be nonconservative in predicting the point of instability; whereas, the T/sub applied/ analysis of Ernst and coworkers appears to be accurate, but requires precision beyond that displayed in this program. The generalized Paris analysis applied to the compact specimen and evaluated at maximum load was most consistent in predicting instability. 16 figures, 3 tables

  15. Condensin II mutation causes T-cell lymphoma through tissue-specific genome instability

    Science.gov (United States)

    Woodward, Jessica; Taylor, Gillian C.; Soares, Dinesh C.; Boyle, Shelagh; Sie, Daoud; Read, David; Chathoth, Keerthi; Vukovic, Milica; Tarrats, Nuria; Jamieson, David; Campbell, Kirsteen J.; Blyth, Karen; Acosta, Juan Carlos; Ylstra, Bauke; Arends, Mark J.; Kranc, Kamil R.; Jackson, Andrew P.; Bickmore, Wendy A.

    2016-01-01

    Chromosomal instability is a hallmark of cancer, but mitotic regulators are rarely mutated in tumors. Mutations in the condensin complexes, which restructure chromosomes to facilitate segregation during mitosis, are significantly enriched in cancer genomes, but experimental evidence implicating condensin dysfunction in tumorigenesis is lacking. We report that mice inheriting missense mutations in a condensin II subunit (Caph2nes) develop T-cell lymphoma. Before tumors develop, we found that the same Caph2 mutation impairs ploidy maintenance to a different extent in different hematopoietic cell types, with ploidy most severely perturbed at the CD4+CD8+ T-cell stage from which tumors initiate. Premalignant CD4+CD8+ T cells show persistent catenations during chromosome segregation, triggering DNA damage in diploid daughter cells and elevated ploidy. Genome sequencing revealed that Caph2 single-mutant tumors are near diploid but carry deletions spanning tumor suppressor genes, whereas P53 inactivation allowed Caph2 mutant cells with whole-chromosome gains and structural rearrangements to form highly aggressive disease. Together, our data challenge the view that mitotic chromosome formation is an invariant process during development and provide evidence that defective mitotic chromosome structure can promote tumorigenesis. PMID:27737961

  16. Secondary knee instability caused by fracture of the stabilizing insert in a dual-articular total knee

    DEFF Research Database (Denmark)

    Boesen, Morten P; Jensen, Tim Toftgaard; Husted, Henrik

    2004-01-01

    A case of a fractured polyethylene stabilizing insert causing secondary knee instability in a Dual-articular total knee arthroplasty (TKA) is presented. A 65-year-old woman who underwent surgery with a Dual-articular TKA 4 years earlier had a well-functioning prosthesis until a fall, after which......-articular knee....

  17. Morphological instability of Ag films caused by phase transition in the underlying Ta barrier layer

    Energy Technology Data Exchange (ETDEWEB)

    Mardani, Shabnam, E-mail: shabnam.mardani@angstrom.uu.se; Vallin, Örjan; Wätjen, Jörn Timo; Norström, Hans; Olsson, Jörgen; Zhang, Shi-Li, E-mail: shili.zhang@angstrom.uu.se [Solid State Electronics, The Ångström Laboratory, Uppsala University, P.O. Box 534, SE-75121 (Sweden)

    2014-08-18

    Wide-bandgap (WBG) semiconductor technologies are maturing and may provide increased device performance in many fields of applications, such as high-temperature electronics. However, there are still issues regarding the stability and reliability of WBG devices. Of particular importance is the high-temperature stability of interconnects for electronic systems based on WBG-semiconductors. For metallization without proper encapsulation, morphological degradation can occur at elevated temperatures. Sandwiching Ag films between Ta and/or TaN layers in this study is found to be electrically and morphologically stabilize the Ag metallization up to 800 °C, compared to 600 °C for uncapped films. However, the barrier layer plays a key role and TaN is found to be superior to Ta, resulting in the best achieved stability, whereas the difference between Ta and TaN caps is negligible. The β-to-α phase transition in the underlying Ta barrier layer is identified as the major cause responsible for the morphological instability observed above 600 °C. It is shown that this phase transition can be avoided using a stacked Ta/TaN barrier.

  18. QUASI-BIENNIAL OSCILLATIONS IN THE SOLAR TACHOCLINE CAUSED BY MAGNETIC ROSSBY WAVE INSTABILITIES

    International Nuclear Information System (INIS)

    Zaqarashvili, Teimuraz V.; Carbonell, Marc; Oliver, Ramon; Ballester, Jose Luis

    2010-01-01

    Quasi-biennial oscillations (QBOs) are frequently observed in solar activity indices. However, no clear physical mechanism for the observed variations has been suggested so far. Here, we study the stability of magnetic Rossby waves in the solar tachocline using the shallow water magnetohydrodynamic approximation. Our analysis shows that the combination of typical differential rotation and a toroidal magnetic field with a strength of ≥10 5 G triggers the instability of the m = 1 magnetic Rossby wave harmonic with a period of ∼2 years. This harmonic is antisymmetric with respect to the equator and its period (and growth rate) depends on the differential rotation parameters and magnetic field strength. The oscillations may cause a periodic magnetic flux emergence at the solar surface and consequently may lead to the observed QBO in solar activity features. The period of QBOs may change throughout a cycle, and from cycle to cycle, due to variations of the mean magnetic field and differential rotation in the tachocline.

  19. Structures for common-cause failure analysis

    International Nuclear Information System (INIS)

    Vaurio, J.K.

    1981-01-01

    Common-cause failure methodology and terminology have been reviewed and structured to provide a systematical basis for addressing and developing models and methods for quantification. The structure is based on (1) a specific set of definitions, (2) categories based on the way faults are attributable to a common cause, and (3) classes based on the time of entry and the time of elimination of the faults. The failure events are then characterized by their likelihood or frequency and the average residence time. The structure provides a basis for selecting computational models, collecting and evaluating data and assessing the importance of various failure types, and for developing effective defences against common-cause failure. The relationships of this and several other structures are described

  20. Plathelminth abundance in North Sea salt marshes: environmental instability causes high diversity

    Science.gov (United States)

    Armonies, Werner

    1986-09-01

    Although supralittoral salt marshes are habitats of high environmental instability, the meiofauna is rich in species and abundance is high. The community structure of free-living Plathelminthes (Turbellaria) in these salt marshes is described. On an average, 104 individuals are found below an area of 10 cm2. The average species density in ungrazed salt marshes is 11.3 below 10 cm2 and 45.2 below 100 cm2, indicating strong small-scale heterogenity. The faunal similarity between sediment and the corresponding above-ground vegetation is higher than between adjacent sample sites. Species prefer distinct ranges of salinity. In the lower part of the supralittoral salt marshes, the annual fluctuations of salinity are strongest and highly unpredictable. This region is richest in plathelminth species and abundance; diversity is highest, and the faunal composition of parallel samples is quite similar. In the upper part of the supralittoral salt marshes, the annual variability of salinity is lower, plathelminths are poor in species diversity and abundance. Parallel samples often have no species in common. Thus, those salt marsh regions with the most unstable environment are inhabited by the most diverse species assemblage. Compared to other littoral zones of the North Sea, however, plathelminth diversity in salt marshes is low. The observed plathelminth diversity pattern can apparently be explained by the “dynamic equilibrium model” (Huston, 1979).

  1. Regularized Estimation of Structural Instability in Factor Models: The US Macroeconomy and the Great Moderation

    DEFF Research Database (Denmark)

    Callot, Laurent; Kristensen, Johannes Tang

    This paper shows that the parsimoniously time-varying methodology of Callot and Kristensen (2015) can be applied to factor models.We apply this method to study macroeconomic instability in the US from 1959:1 to 2006:4 with a particular focus on the Great Moderation. Models with parsimoniously time...... that the parameters of both models exhibit a higher degree of instability in the period from 1970:1 to 1984:4 relative to the following 15 years. In our setting the Great Moderation appears as the gradual ending of a period of high structural instability that took place in the 1970s and early 1980s....

  2. Family Structure Transitions and Child Development: Instability, Selection, and Population Heterogeneity

    OpenAIRE

    Lee, Dohoon; McLanahan, Sara

    2015-01-01

    A growing literature documents the importance of family instability for child wellbeing. In this article, we use longitudinal data from the Fragile Families and Child Wellbeing Study to examine the impacts of family instability on children’s cognitive and socioemotional development in early and middle childhood. We extend existing research in several ways: (1) by distinguishing between the number and types of family structure changes; (2) by accounting for time-varying as well as time-constan...

  3. Causes of genome instability: the effect of low dose chemical exposures in modern society

    Science.gov (United States)

    Langie, Sabine A.S.; Koppen, Gudrun; Desaulniers, Daniel; Al-Mulla, Fahd; Al-Temaimi, Rabeah; Amedei, Amedeo; Azqueta, Amaya; Bisson, William H.; Brown, Dustin; Brunborg, Gunnar; Charles, Amelia K.; Chen, Tao; Colacci, Annamaria; Darroudi, Firouz; Forte, Stefano; Gonzalez, Laetitia; Hamid, Roslida A.; Knudsen, Lisbeth E.; Leyns, Luc; Lopez de Cerain Salsamendi, Adela; Memeo, Lorenzo; Mondello, Chiara; Mothersill, Carmel; Olsen, Ann-Karin; Pavanello, Sofia; Raju, Jayadev; Rojas, Emilio; Roy, Rabindra; Ryan, Elizabeth; Ostrosky-Wegman, Patricia; Salem, Hosni K.; Scovassi, Ivana; Singh, Neetu; Vaccari, Monica; Van Schooten, Frederik J.; Valverde, Mahara; Woodrick, Jordan; Zhang, Luoping; van Larebeke, Nik; Kirsch-Volders, Micheline; Collins, Andrew R.

    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, genome instability can be defined as an enhanced tendency for the genome to acquire mutations; ranging from changes to the nucleotide sequence to chromosomal gain, rearrangements or loss. This review raises the hypothesis that in addition to known human carcinogens, exposure to low dose of other chemicals present in our modern society could contribute to carcinogenesis by indirectly affecting genome stability. The selected chemicals with their mechanisms of action proposed to indirectly contribute to genome instability are: heavy metals (DNA repair, epigenetic modification, DNA damage signaling, telomere length), acrylamide (DNA repair, chromosome segregation), bisphenol A (epigenetic modification, DNA damage signaling, mitochondrial function, chromosome segregation), benomyl (chromosome segregation), quinones (epigenetic modification) and nano-sized particles (epigenetic pathways, mitochondrial function, chromosome segregation, telomere length). The purpose of this review is to describe the crucial aspects of genome instability, to outline the ways in which environmental chemicals can affect this cancer hallmark and to identify candidate chemicals for further study. The overall aim is to make scientists aware of the increasing need to unravel the underlying mechanisms via which chemicals at low doses can induce genome instability and thus promote carcinogenesis. PMID:26106144

  4. Loss of RMI2 Increases Genome Instability and Causes a Bloom-Like Syndrome.

    Directory of Open Access Journals (Sweden)

    Damien F Hudson

    2016-12-01

    Full Text Available Bloom syndrome is a recessive human genetic disorder with features of genome instability, growth deficiency and predisposition to cancer. The only known causative gene is the BLM helicase that is a member of a protein complex along with topoisomerase III alpha, RMI1 and 2, which maintains replication fork stability and dissolves double Holliday junctions to prevent genome instability. Here we report the identification of a second gene, RMI2, that is deleted in affected siblings with Bloom-like features. Cells from homozygous individuals exhibit elevated rates of sister chromatid exchange, anaphase DNA bridges and micronuclei. Similar genome and chromosome instability phenotypes are observed in independently derived RMI2 knockout cells. In both patient and knockout cell lines reduced localisation of BLM to ultra fine DNA bridges and FANCD2 at foci linking bridges are observed. Overall, loss of RMI2 produces a partially active BLM complex with mild features of Bloom syndrome.

  5. Germ-line CAG repeat instability causes extreme CAG repeat expansion with infantile-onset spinocerebellar ataxia type 2

    DEFF Research Database (Denmark)

    Vinther-Jensen, Tua; Ek, Jakob; Duno, Morten

    2013-01-01

    The spinocerebellar ataxias (SCA) are a genetically and clinically heterogeneous group of diseases, characterized by dominant inheritance, progressive cerebellar ataxia and diverse extracerebellar symptoms. A subgroup of the ataxias is caused by unstable CAG-repeat expansions in their respective ...... of paternal germ-line repeat sequence instability of the expanded SCA2 locus.European Journal of Human Genetics advance online publication, 10 October 2012; doi:10.1038/ejhg.2012.231....

  6. Contact Line Instability Caused by Air Rim Formation under Nonsplashing Droplets.

    Science.gov (United States)

    Pack, Min; Kaneelil, Paul; Kim, Hyoungsoo; Sun, Ying

    2018-05-01

    Drop impact is fundamental to various natural and industrial processes such as rain-induced soil erosion and spray-coating technologies. The recent discovery of the role of air entrainment between the droplet and the impacting surface has produced numerous works, uncovering the unique physics that correlates the air film dynamics with the drop impact outcomes. In this study, we focus on the post-failure air entrainment dynamics for We numbers well below the splash threshold under different ambient pressures and elucidate the interfacial instabilities formed by air entrainment at the wetting front of impacting droplets on perfectly smooth, viscous films of constant thickness. A high-speed total internal reflection microscopy technique accounting for the Fresnel reflection at the drop-air interface allows for in situ measurements of an entrained air rim at the wetting front. The presence of an air rim is found to be a prerequisite to the interfacial instability which is formed when the capillary pressure in the vicinity of the contact line can no longer balance the increasing gas pressure near the wetting front. A critical capillary number for the air rim formation is experimentally identified above which the wetting front becomes unstable where this critical capillary number inversely scales with the ambient pressure. The contact line instabilities at relatively low We numbers ( We ∼ O(10)) observed in this study provide insight into the conventional understanding of hydrodynamic instabilities under drop impact which usually require We ≫ 10.

  7. Nucleation of frictional instability caused by fluid pressurization in subducted blueschist

    NARCIS (Netherlands)

    Sawai, M.; Niemeijer, A.R.; Plümper, O.; Hirose, T.; Spiers, C.J.

    2016-01-01

    Pore pressure is an important factor in controlling the slip instability of faults and thus the generation of earthquakes. Particularly slow earthquakes are widespread in subduction zones and usually linked to the occurrence of high pore pressure. Yet the influence of fluid pressure and effective

  8. Multi-dimensional instability of electrostatic solitary structures in magnetized nonthermal dusty plasmas

    International Nuclear Information System (INIS)

    Mamun, A.A.; Russel, S.M.; Mendoza-Briceno, C.A.; Alam, M.N.; Datta, T.K.; Das, A.K.

    1999-05-01

    A rigorous theoretical investigation has been made of multi-dimensional instability of obliquely propagating electrostatic solitary structures in a hot magnetized nonthermal dusty plasma which consists of a negatively charged hot dust fluid, Boltzmann distributed electrons, and nonthermally distributed ions. The Zakharov-Kuznetsov equation for the electrostatic solitary structures that exist in such a dusty plasma system is derived by the reductive perturbation method. The multi-dimensional instability of these solitary waves is also studied by the small-k (long wavelength plane wave) perturbation expansion method. The nature of these solitary structures, the instability criterion, and their growth rate depending on dust-temperature, external magnetic field, and obliqueness are discussed. The implications of these results to some space and astrophysical dusty plasma situations are briefly mentioned. (author)

  9. Macroparticle model for longitudinal emittance growth caused by negative mass instability in a proton synchrotron

    CERN Document Server

    MacLachlan, J A

    2004-01-01

    Both theoretical models and beam observations of negative mass instability fall short of a full description of the dynamics and the dynamical effects. Clarification by numerical modeling is now practicable because of the recent proliferation of so-called computing farms. The results of modeling reported in this paper disagree with some predictions based on a long-standing linear perturbation calculation. Validity checks on the macroparticle model are described.

  10. Sausage mode instability of thin current sheets as a cause of magnetospheric substorms

    Directory of Open Access Journals (Sweden)

    J. Büchner

    Full Text Available Observations have shown that, prior to substorm explosions, thin current sheets are formed in the plasma sheet of the Earth's magnetotail. This provokes the question, to what extent current-sheet thinning and substorm onsets are physically, maybe even causally, related. To answer this question, one has to understand the plasma stability of thin current sheets. Kinetic effects must be taken into account since particle scales are reached in the course of tail current-sheet thinning. We present the results of theoretical investigations of the stability of thin current sheets and about the most unstable mode of their decay. Our conclusions are based upon a non-local linear dispersion analysis of a cross-magnetic field instability of Harris-type current sheets. We found that a sausage-mode bulk current instability starts after a sheet has thinned down to the ion inertial length. We also present the results of three-dimensional electromagnetic PIC-code simulations carried out for mass ratios up to Mi / me=64. They verify the linearly predicted properties of the sausage mode decay of thin current sheets in the parameter range of interest.

    Key words. Magnetospheric physics (plasma waves and instabilities; storms and substorms · Space plasma physics (magnetic reconnection

  11. Material instabilities and their role for the initiation of boudinage and folding structures

    Science.gov (United States)

    Veveakis, Manolis; Peters, Max; Poulet, Thomas; Karrech, Ali; Herwegh, Marco; Regenauer-Lieb, Klaus

    2015-04-01

    Localized phenomena, such as pinch-and-swell boudinage or localized folds, are usually interpreted to arise from viscosity contrasts. These are caused by structural heterogeneities, such as geometric or material imperfections. An alternative possibility for strain localization exists in material science, where dynamic localization emerges out of a steady state for a given critical set of material parameters and loading rates (Montési and Zuber, 2002). In our contribution, we will investigate the conditions under which this type of instabilities triggers localized deformation. Moreover, we discuss whether geological materials necessarily require structural heterogeneities, such as weak seeds, in order to generate aforementioned localized structures. We set up a random distribution of grain sizes in a layer embedded in a matrix with a diffusion creep rheology. Deformation within the layer is accommodated by dislocation and diffusion creep as end member deformation mechanism. The grain size evolution follows the paleowattmeter scaling relationship for calcite creep (Austin and Evans, 2007), which is controlled by thermo-mechanical feedbacks (Herwegh et al., 2014). During the first strain increments in the numerical simulation, the layer establishes a viscous steady state, which is the systems' response to optimize energy following the paleowattmeter (Herwegh et al., 2014). With further loading, localization interestingly arises out of a homogeneous state. We will demonstrate the robustness of this numerical solution by identifying the natural mode shapes and frequencies of the simulated structure and material parameters, including geometric imperfections (Rudnicki and Rice, 1975). This technique aims at the determination of the spatial manifestation of the instability pattern (Peters et al., in review). The eigenvalues are thought to represent the nodal points, where the onset of (visco)-elasto-plastic localization can initiate in the structure (Rudnicki and Rice

  12. Family Structure Transitions and Child Development: Instability, Selection, and Population Heterogeneity.

    Science.gov (United States)

    Lee, Dohoon; McLanahan, Sara

    2015-08-01

    A growing literature documents the importance of family instability for child wellbeing. In this article, we use longitudinal data from the Fragile Families and Child Wellbeing Study to examine the impacts of family instability on children's cognitive and socioemotional development in early and middle childhood. We extend existing research in several ways: (1) by distinguishing between the number and types of family structure changes; (2) by accounting for time-varying as well as time-constant confounding; and (3) by assessing racial/ethnic and gender differences in family instability effects. Our results indicate that family instability has a causal effect on children's development, but the effect depends on the type of change, the outcome assessed, and the population examined. Generally speaking, transitions out of a two-parent family are more negative for children's development than transitions into a two-parent family. The effect of family instability is stronger for children's socioemotional development than for their cognitive achievement. For socioemotional development, transitions out of a two-parent family are more negative for white children, whereas transitions into a two-parent family are more negative for Hispanic children. These findings suggest that future research should pay more attention to the type of family structure transition and to population heterogeneity.

  13. Genomic instability following irradiation

    International Nuclear Information System (INIS)

    Hacker-Klom, U.B.; Goehde, W.

    2001-01-01

    Ionising irradiation may induce genomic instability. The broad spectrum of stress reactions in eukaryontic cells to irradiation complicates the discovery of cellular targets and pathways inducing genomic instability. Irradiation may initiate genomic instability by deletion of genes controlling stability, by induction of genes stimulating instability and/or by activating endogeneous cellular viruses. Alternatively or additionally it is discussed that the initiation of genomic instability may be a consequence of radiation or other agents independently of DNA damage implying non nuclear targets, e.g. signal cascades. As a further mechanism possibly involved our own results may suggest radiation-induced changes in chromatin structure. Once initiated the process of genomic instability probably is perpetuated by endogeneous processes necessary for proliferation. Genomic instability may be a cause or a consequence of the neoplastic phenotype. As a conclusion from the data available up to now a new interpretation of low level radiation effects for radiation protection and in radiotherapy appears useful. The detection of the molecular mechanisms of genomic instability will be important in this context and may contribute to a better understanding of phenomenons occurring at low doses <10 cSv which are not well understood up to now. (orig.)

  14. Electronic instabilities and structural fluctuations in self-assembled atom wires

    NARCIS (Netherlands)

    Snijders, P.C.

    2006-01-01

    One-dimensional (1D) solid state systems can behave drastically different from their higher dimensional counterparts. Increased interactions can produce electronic and/or structural instabilities. In this respect, the following fundamental questions are important for a proper understanding of the

  15. DHX9 helicase is involved in preventing genomic instability induced by alternatively structured DNA in human cells.

    Science.gov (United States)

    Jain, Aklank; Bacolla, Albino; Del Mundo, Imee M; Zhao, Junhua; Wang, Guliang; Vasquez, Karen M

    2013-12-01

    Sequences that have the capacity to adopt alternative (i.e. non-B) DNA structures in the human genome have been implicated in stimulating genomic instability. Previously, we found that a naturally occurring intra-molecular triplex (H-DNA) caused genetic instability in mammals largely in the form of DNA double-strand breaks. Thus, it is of interest to determine the mechanism(s) involved in processing H-DNA. Recently, we demonstrated that human DHX9 helicase preferentially unwinds inter-molecular triplex DNA in vitro. Herein, we used a mutation-reporter system containing H-DNA to examine the relevance of DHX9 activity on naturally occurring H-DNA structures in human cells. We found that H-DNA significantly increased mutagenesis in small-interfering siRNA-treated, DHX9-depleted cells, affecting mostly deletions. Moreover, DHX9 associated with H-DNA in the context of supercoiled plasmids. To further investigate the role of DHX9 in the recognition/processing of H-DNA, we performed binding assays in vitro and chromatin immunoprecipitation assays in U2OS cells. DHX9 recognized H-DNA, as evidenced by its binding to the H-DNA structure and enrichment at the H-DNA region compared with a control region in human cells. These composite data implicate DHX9 in processing H-DNA structures in vivo and support its role in the overall maintenance of genomic stability at sites of alternatively structured DNA.

  16. Outbreeding causes developmental instability in Drosophila subobscura

    DEFF Research Database (Denmark)

    Kurbalija, Zorana; Stamenkovic-Radak, Marina; Pertoldi, C.

    2010-01-01

    A possible effect of interpopulation hybridization is either outbreeding depression, as a consequence of breakdown of coadapted gene complexes which can increase developmental instability (DI) of the traits, or increased heterozygosity, which can reduce DI. One of the principal methods commonly...... used to estimate DI is the variability of fluctuating asymmetry (FA). We analysed the effect of interpopulation hybridization in Drosophila subobscura through the variability in the wing size and the FA of wing length and width for both sexes in parental, F1 and F2 generations. The results of the wing...... size per se in intra- and interpopulation hybrids of D. subobscura do not explicitly reveal the significance of either of the two hypotheses. However, the results of the FA of the wing traits give a different insight. The FA of wing length and width generally increases in interpopulation crosses in F1...

  17. Identifying the underlying causes of biological instability in a full-scale drinking water supply system.

    Science.gov (United States)

    Nescerecka, Alina; Juhna, Talis; Hammes, Frederik

    2018-05-15

    Changes in bacterial concentration and composition in drinking water during distribution are often attributed to biological (in)stability. Here we assessed temporal biological stability in a full-scale distribution network (DN) supplied with different types of source water: treated and chlorinated surface water and chlorinated groundwater produced at three water treatment plants (WTP). Monitoring was performed weekly during 12 months in two locations in the DN. Flow cytometric total and intact cell concentration (ICC) measurements showed considerable seasonal fluctuations, which were different for two locations. ICC varied between 0.1-3.75 × 10 5  cells mL -1 and 0.69-4.37 × 10 5  cells mL -1 at two locations respectively, with ICC increases attributed to temperature-dependent bacterial growth during distribution. Chlorinated water from the different WTP was further analysed with a modified growth potential method, identifying primary and secondary growth limiting compounds. It was observed that bacterial growth in the surface water sample after chlorination was primarily inhibited by phosphorus limitation and secondly by organic carbon limitation, while carbon was limiting in the chlorinated groundwater samples. However, the ratio of available nutrients changed during distribution, and together with disinfection residual decay, this resulted in higher bacterial growth potential detected in the DN than at the WTP. In this study, bacterial growth was found to be higher (i) at higher water temperatures, (ii) in samples with lower chlorine residuals and (iii) in samples with less nutrient (carbon, phosphorus, nitrogen, iron) limitation, while this was significantly different between the samples of different origin. Thus drinking water microbiological quality and biological stability could change during different seasons, and the extent of these changes depends on water temperature, the water source and treatment. Furthermore, differences in primary

  18. Nonlinear Dynamics Mechanism of Rock Burst Induced by the Instability of the Layer-Crack Plate Structure in the Coal Wall in Deep Coal Mining

    Directory of Open Access Journals (Sweden)

    Yanlong Chen

    2017-01-01

    Full Text Available The instability of layer-crack plate structure in coal wall is one of the causes of rock burst. In the present paper, we investigate the formation and instability processes of layer-crack plate structure in coal wall by experiments and theoretical analysis. The results reveal that layer-crack plate structure formed near the free surface of the coal wall during the loading. During the formation of the layer-crack plate structure, the lateral displacement curve of the coal wall experiences a jagged variation, which suggests the nonlinear instability failure of the coal wall with a sudden release of the elastic energy. Then, a dynamic model for the stability analysis of the layer-crack plate structure was proposed, which takes consideration of the dynamic disturbance factor. Based on the dynamic model, the criterion for dynamic instability of the layer-crack plate structure was determined and demonstrated by an example. According to the analytical results, some control methods of dynamic stability of the layer-crack plate structure was put forward.

  19. The electron-electron instability in a spherical plasma structure with an intermediate double layer

    International Nuclear Information System (INIS)

    Lapuerta, V.; Ahedo, E.

    2003-01-01

    A linear dynamic model of a spherical plasma structure with an intermediate double layer is analyzed in the high-frequency range. The two ion populations tend to stay frozen in their stationary response and this prevents the displacement of the double layer. Different electron modes dominate the plasma dynamics in each quasineutral region. The electrostatic potential and the electron current are the magnitudes most perturbed. The structure develops a reactive electron-electron instability, which is made up of a countable family of eigenmodes. Space-charge effects must be included in the quasineutral regions to determine the eigenmode carrying the maximum growth rate. Except for very small Debye lengths, the fundamental eigenmode governs the instability. The growth rate for the higher harmonics approaches that of an infinite plasma. The instability modes develop mainly on the plasma at the high-potential side of the double layer. The influence of the parameters defining the stationary solution on the instability growth rate is investigated, and the parametric regions of stability are found. The comparison with a couple of experiments on plasma contactors is satisfactory

  20. Structural instabilities in superconductor Y-Ba-Cu-O studied by positron annihilation

    International Nuclear Information System (INIS)

    Wang Shaojie; Li Xiaohua; Chen Yilong; Li Shiqing; Feng Guohua; Wang Zhu; Chen Ang; Li Biaorong

    1989-01-01

    The positron lifetime and Doppler broadening were measured as a function of temperature between 100K and 300K for Y-Ba-Cu-O superconductor. There are anomalous changes in the positron lifetimes and S parameters near 130K and 260K which imply that some phase transitions related to superconductivity happenned there. The results were discussed in terms of the lattice instabilities which may caused by the ordering readjustment of oxygen vacancies

  1. Family Structure, Maternal Dating, and Sexual Debut: Extending the Conceptualization of Instability.

    Science.gov (United States)

    Zito, Rena Cornell; De Coster, Stacy

    2016-05-01

    Family structure influences the risk of early onset of sexual intercourse. This study proposes that the family structures associated with risk-single-mother, step-parent, and cohabiting-influence early sexual debut due to family instability, including shifts in family structure and maternal dating, which can undermine parental control and transmit messages about the acceptability of nonmarital sex. Previous research has not considered maternal dating as a component of family instability, assuming single mothers who date and those who do not date experience comparable levels of family disruption and transmit similar messages about the acceptability of nonmarital sex. Hypotheses are assessed using logistic regression models predicting the odds of early onset of sexual intercourse among 9959 respondents (53 % female, 47 % male) from the National Longitudinal Study of Adolescent to Adult Health. Respondents were ages 12-17 at the first wave of data collection and 18-26 at the third wave, when respondents reported the age at which they first had sexual intercourse. Results show that maternal dating is a source of family instability with repercussions for early sexual debut. Parental control and permissive attitudes towards teenage sex and pregnancy link at-risk family structures and maternal dating to early sexual initiation among females, though these variables do not fully explain family structure and maternal dating effects. Among males, the influence of maternal dating on early sexual debut is fully explained by the learning of permissive sexual attitudes.

  2. Flutter instability of cantilevered carbon nanotubes caused by magnetic fluid flow subjected to a longitudinal magnetic field

    Science.gov (United States)

    Sadeghi-Goughari, Moslem; Jeon, Soo; Kwon, Hyock-Ju

    2018-04-01

    CNT (Carbon nanotube)-based fluidic systems hold a great potential for emerging medical applications such as drug delivery for cancer therapy. CNTs can be used to deliver anticancer drugs into a target site under a magnetic field guidance. One of the critical issues in designing such systems is how to avoid the vibration induced by the fluid flow, which is undesirable and may even promote the structural instability. The main objective of the present research is to develop a fluid structure interaction (FSI) model to investigate the flutter instability of a cantilevered CNT induced by a magnetic fluid flow under a longitudinal magnetic field. The CNT is assumed to be embedded in a viscoelastic matrix to consider the effect of biological medium around it. To obtain a dynamical model for the system, the Navier-Stokes theory of magnetic-fluid flow is coupled to the Euler-Bernoulli beam model for CNT. The small size effects of the magnetic fluid and CNT are considered through the small scale parameters including Knudsen number (Kn) and the nonlocal parameter. Then, the extended Galerkin's method is applied to solve the FSI governing equations, and to derive the stability diagrams of the system. Results show how the magnetic properties of the fluid flow have an effect on improving the stability of the cantilevered CNT by increasing the flutter velocity.

  3. Structural instability and ground state of the U{sub 2}Mo compound

    Energy Technology Data Exchange (ETDEWEB)

    Losada, E.L., E-mail: losada@cab.cnea.gov.ar [SIM" 3, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica (Argentina); Garcés, J.E. [Gerencia de Investigación y Aplicaciones Nucleares, Comisión Nacional de Energía Atómica (Argentina)

    2015-11-15

    This work reports on the structural instability at T = 0 °K of the U{sub 2}Mo compound in the C11{sub b} structure under the distortion related to the C{sub 66} elastic constant. The electronic properties of U{sub 2}Mo such as density of states (DOS), bands and Fermi surface (FS) are studied to understand the source of the instability. The C11{sub b} structure can be interpreted as formed by parallel linear chains along the z-directions each one composed of successive U–Mo–U blocks. Hybridization due to electronic interactions inside the U–Mo–U blocks is slightly modified under the D{sub 6} distortion. The change in distance between chains modifies the U–U interaction and produces a split of f-states. The distorted structure is stabilized by a decrease in energy of the hybridized states, mainly between d-Mo and f-U states, together with the f-band split. Consequently, an induced Peierls distortion is produced in U{sub 2}Mo due to the D{sub 6} distortion. It is important to note that the results of this work indicate that the structure of the ground state of the U{sub 2}Mo compound is not the assumed C11{sub b} structure. It is suggested for the ground state a structure with hexagonal symmetry (P6 #168), ∼0.1 mRy below the energy of the recently proposed Pmmn structure. - Highlights: • Structural instability of the C11b compound due to the D6 deformation. • Induced Peierls distortion due to the D6 deformation. • Distorted structure is stabilized by hybridization and split of f-Uranium state. • P6 (#168) suggested ground state for the U{sub 2}Mo compound.

  4. Structural instability and ground state of the U_2Mo compound

    International Nuclear Information System (INIS)

    Losada, E.L.; Garcés, J.E.

    2015-01-01

    This work reports on the structural instability at T = 0 °K of the U_2Mo compound in the C11_b structure under the distortion related to the C_6_6 elastic constant. The electronic properties of U_2Mo such as density of states (DOS), bands and Fermi surface (FS) are studied to understand the source of the instability. The C11_b structure can be interpreted as formed by parallel linear chains along the z-directions each one composed of successive U–Mo–U blocks. Hybridization due to electronic interactions inside the U–Mo–U blocks is slightly modified under the D_6 distortion. The change in distance between chains modifies the U–U interaction and produces a split of f-states. The distorted structure is stabilized by a decrease in energy of the hybridized states, mainly between d-Mo and f-U states, together with the f-band split. Consequently, an induced Peierls distortion is produced in U_2Mo due to the D_6 distortion. It is important to note that the results of this work indicate that the structure of the ground state of the U_2Mo compound is not the assumed C11_b structure. It is suggested for the ground state a structure with hexagonal symmetry (P6 #168), ∼0.1 mRy below the energy of the recently proposed Pmmn structure. - Highlights: • Structural instability of the C11b compound due to the D6 deformation. • Induced Peierls distortion due to the D6 deformation. • Distorted structure is stabilized by hybridization and split of f-Uranium state. • P6 (#168) suggested ground state for the U_2Mo compound.

  5. Effects of Convective Transport of Solute and Impurities on Defect-Causing Kinetics Instabilities

    Science.gov (United States)

    Vekilov, Peter G.; Higginbotham, Henry Keith (Technical Monitor)

    2001-01-01

    For in-situ studies of the formation and evolution of step patterns during the growth of protein crystals, we have designed and assembled an experimental setup based on Michelson interferometry with the surface of the growing protein crystal as one of the reflective surfaces. The crystallization part of the device allows optical monitoring of a face of a crystal growing at temperature stable within 0.05 C in a developed solution flow of controlled direction and speed. The reference arm of the interferometer contains a liquid-crystal element that allows controlled shifts of the phase of the interferograms. We employ an image processing algorithm which combines five images with a pi/2 phase difference between each pair of images. The images are transferred to a computer by a camera capable of capturing 6-8 frames per second. The device allows data collection data regarding growth over a relatively large area (approximately .3 sq. mm) in-situ and in real time during growth. The estimated dept resolution of the phase shifting interferometry is about 100 A. The lateral resolution, depending on the zoom ratio, varies between 0.3 and 0.6 micrometers. We have now collected quantitative results on the onset, initial stages and development of instabilities in moving step trains on vicinal crystal surfaces at varying supersaturation, position on the facet, crystal size and temperature with the proteins ferritin, apoferritin and thaumatin. Comparisons with theory, especially with the AFM results on the molecular level processes, see below, allow tests of the rational for the effects of convective flows and, as a particular case, the lack thereof, on step bunching.

  6. Coherent structures in ablatively compressed ICF targets and Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Pant, H.C.; Desai, T.

    1996-01-01

    One of the major issues in laser induced inertial confinement fusion (ICF) is a stable ablative compression of spherical fusion pellets. The main impediment in achievement of this objective is Rayleigh-Taylor instability at the pellet's ablation front. Under sufficiently high acceleration this instability can grow out of noise. However, it can also arise either due to non-uniform laser intensity distribution over the pellet surface or due to pellet wall areal mass irregularity. Coherent structures in the dense target behind the ablation front can be effectively utilised for stabilisation of the Rayleigh-Taylor phenomenon. Such coherent structures in the form of a super lattice can be created by doping the pellet pusher with high atomic number (Z) micro particles. A compressed-cool pusher under laser irradiation behaves like a strongly correlated non ideal plasma when compressed to sufficiently high density such that the non ideality parameter exceeds unity. Moreover, the nonideality parameter for high Z microinclusions may exceed a critical value of 180 and as a consequence they remain in the form of intact clusters, maintaining the superlattice intact during ablative acceleration. Micro-hetrogeneity and its superlattice plays an important role in stabilization of Rayleigh-Taylor instability, through a variety of mechanisms. (orig.)

  7. Global chromosomal structural instability in a subpopulation of starving Escherichia coli cells.

    Directory of Open Access Journals (Sweden)

    Dongxu Lin

    2011-08-01

    Full Text Available Copy-number variations (CNVs constitute very common differences between individual humans and possibly all genomes and may therefore be important fuel for evolution, yet how they form remains elusive. In starving Escherichia coli, gene amplification is induced by stress, controlled by the general stress response. Amplification has been detected only encompassing genes that confer a growth advantage when amplified. We studied the structure of stress-induced gene amplification in starving cells in the Lac assay in Escherichia coli by array comparative genomic hybridization (aCGH, with polymerase chain reaction (pcr and DNA sequencing to establish the structures generated. About 10% of 300 amplified isolates carried other chromosomal structural change in addition to amplification. Most of these were inversions and duplications associated with the amplification event. This complexity supports a mechanism similar to that seen in human non-recurrent copy number variants. We interpret these complex events in terms of repeated template switching during DNA replication. Importantly, we found a significant occurrence (6 out of 300 of chromosomal structural changes that were apparently not involved in the amplification event. These secondary changes were absent from 240 samples derived from starved cells not carrying amplification, suggesting that amplification happens in a differentiated subpopulation of stressed cells licensed for global chromosomal structural change and genomic instability. These data imply that chromosomal structural changes occur in bursts or showers of instability that may have the potential to drive rapid evolution.

  8. Phase instability of alloys caused by transmutation effects during neutron irradiation

    International Nuclear Information System (INIS)

    Platov, Yu.M.; Pletnev, M.N.

    1994-01-01

    A theory of the phase changes in a two-phase binary A-B alloy in the coarsening condition caused by burnout of solute B due to nuclear reactions is presented. It is shown that this burnout process introduces diffusion redistribution of solute between second phase precipitates and solid solution. The burnout induced solute flux away from second phase precipitates to solid solution maintaining the concentration of element B in the vicinity to its solubility limit and stimulates, thus, the second phase particle dissolution. This occurs in addition to a process decreasing their sizes as a result of direct burnout of atoms B in the precipitates. In the framework of the theory developed here, analytical expressions describing time evolution of the precipitate size distributions, changes of mean radius and number density of the precipitates, and second phase dissolution times are obtained. On the basis of these results and numerical calculations for aluminium-scandium alloy, it is shown that the burnout processes can induce essential phase changes, and thus cause significant changes of the properties of irradiated materials at high neutron fluences. ((orig.))

  9. R-loops cause genomic instability in T helper lymphocytes from patients with Wiskott-Aldrich syndrome.

    Science.gov (United States)

    Sarkar, Koustav; Han, Seong-Su; Wen, Kuo-Kuang; Ochs, Hans D; Dupré, Loïc; Seidman, Michael M; Vyas, Yatin M

    2017-12-15

    Wiskott-Aldrich syndrome (WAS), X-linked thrombocytopenia (XLT), and X-linked neutropenia, which are caused by WAS mutations affecting Wiskott-Aldrich syndrome protein (WASp) expression or activity, manifest in immunodeficiency, autoimmunity, genomic instability, and lymphoid and other cancers. WASp supports filamentous actin formation in the cytoplasm and gene transcription in the nucleus. Although the genetic basis for XLT/WAS has been clarified, the relationships between mutant forms of WASp and the diverse features of these disorders remain ill-defined. We sought to define how dysfunctional gene transcription is causally linked to the degree of T H cell deficiency and genomic instability in the XLT/WAS clinical spectrum. In human T H 1- or T H 2-skewing cell culture systems, cotranscriptional R-loops (RNA/DNA duplex and displaced single-stranded DNA) and DNA double-strand breaks (DSBs) were monitored in multiple samples from patients with XLT and WAS and in normal T cells depleted of WASp. WASp deficiency provokes increased R-loops and R-loop-mediated DSBs in T H 1 cells relative to T H 2 cells. Mechanistically, chromatin occupancy of serine 2-unphosphorylated RNA polymerase II is increased, and that of topoisomerase 1, an R-loop preventing factor, is decreased at R-loop-enriched regions of IFNG and TBX21 (T H 1 genes) in T H 1 cells. These aberrations accompany increased unspliced (intron-retained) and decreased spliced mRNA of IFNG and TBX21 but not IL13 (T H 2 gene). Significantly, increased cellular load of R-loops and DSBs, which are normalized on RNaseH1-mediated suppression of ectopic R-loops, inversely correlates with disease severity scores. Transcriptional R-loop imbalance is a novel molecular defect causative in T H 1 immunodeficiency and genomic instability in patients with WAS. The study proposes that cellular R-loop load could be used as a potential biomarker for monitoring symptom severity and prognostic outcome in the XLT-WAS clinical spectrum

  10. Effect of dissipative processes on the dispersion and instability of drift waves in a fine-stratified semiconductor structure

    International Nuclear Information System (INIS)

    Bulgakov, A. A.; Shramkova, O. V.

    2006-01-01

    The damping of waves of the charge carrier density in a periodic semiconductor structure in an external electric field is investigated under the assumption that the period of the structure is much smaller than the electromagnetic radiation wavelength. The threshold conditions for the instability of carrier density waves propagating obliquely to the direction of the electric current are obtained. The existence of a resistive instability that can develop at drift velocities both higher and lower than the plasmon phase velocity is predicted

  11. Effect of dissipative processes on the dispersion and instability of drift waves in a fine-stratified semiconductor structure

    International Nuclear Information System (INIS)

    Bulgakov, A.A.; Shramkova, O.V.

    2006-01-01

    In terms of the assumption that the structure period is essentially shorter than the electromagnetic radiation wavelength one considers attenuation of waves of carrier concentration in a periodic semiconducting structure within an external electric field resulting in drift of different sign carriers. One determined conditions of occurrence of instability of carrier concentration waves propagating orthogonally to current direction. One predicts a resistive instability occurrence of which does not require increase of drift velocity in contrast to phase velocity of a plasmon [ru

  12. Population genetic structure of a centipede species with high levels of developmental instability.

    Directory of Open Access Journals (Sweden)

    Giuseppe Fusco

    Full Text Available European populations of the geophilomorph centipede Haplophilus subterraneus show a high proportion of individuals with morphological anomalies, suggesting high levels of developmental instability. The broad geographic distribution of this phenomenon seems to exclude local environmental causes, but the source of instability is still to be identified. The goal of the present study was to collect quantitative data on the occurrence of phenodeviants in different populations, along with data on the patterns of genetic variation within and between populations, in order to investigate possible association between developmental instability and genetic features. In a sample of 11 populations of H. subterraneus, distributed in western and central Europe, we looked for phenodeviants, in particular with respect to trunk morphology, and studied genetic variation through the genotyping of microsatellite loci. Overall, no support was found to the idea that developmental instability in H. subterraneus is related to a specific patterns of genetic variation, including inbreeding estimates. We identified a major genetic partition that subdivides French populations from the others, and a low divergence among northwestern areas, which are possibly related to the post-glacial recolonization from southern refugia and/or to recent anthropogenic soil displacements. A weak correlation between individual number of leg bearing segments and the occurrence of trunk anomalies seems to support a trade-off between these two developmental traits. These results, complemented by preliminary data on developmental stability in two related species, suggest that the phenomenon has not a simple taxonomic distribution, while it exhibits an apparent localization in central and eastern Europe.

  13. Radial structure of curvature-driven instabilities in a hot-electron plasma

    International Nuclear Information System (INIS)

    Spong, D.A.; Berk, H.L.; Van Dam, J.W.

    1984-01-01

    A nonlocal analysis of curvature-driven instabilities for a hot-electron ring interacting with a warm background plasma has been made. Four different instability modes characteristic of hot-electron plasmas have been examined: the high-frequency hot-electron interchange (at frequencies larger than the ion-cyclotron frequency), the compressional Alfven instability, the interacting background pressure-driven interchange, and the conventional hot-electron interchange (at frequencies below the ion-cyclotron frequency). The decoupling condition between core and hot-electron plasmas has also been examined, and its influence on the background and hot-electron interchange stability boundaries has been studied. The assumed equilibrium plasma profiles and resulting radial mode structure differ somewhat from those used in previous local analytic estimates; however, when the analysis is calibrated to the appropriate effective radial wavelength of the nonlocal calculation, reasonable agreement is obtained. Comparison with recent experimental measurements indicates that certain of these modes may play a role in establishing operating boundaries for the ELMO Bumpy Torus-Scale (EBT-S) experiment. The calculations given here indicate the necessity of having core plasma outside the ring to prevent the destabilizing wave resonance of the precessional mode with a cold plasma

  14. Electron-density critical points analysis and catastrophe theory to forecast structure instability in periodic solids.

    Science.gov (United States)

    Merli, Marcello; Pavese, Alessandro

    2018-03-01

    The critical points analysis of electron density, i.e. ρ(x), from ab initio calculations is used in combination with the catastrophe theory to show a correlation between ρ(x) topology and the appearance of instability that may lead to transformations of crystal structures, as a function of pressure/temperature. In particular, this study focuses on the evolution of coalescing non-degenerate critical points, i.e. such that ∇ρ(x c ) = 0 and λ 1 , λ 2 , λ 3 ≠ 0 [λ being the eigenvalues of the Hessian of ρ(x) at x c ], towards degenerate critical points, i.e. ∇ρ(x c ) = 0 and at least one λ equal to zero. The catastrophe theory formalism provides a mathematical tool to model ρ(x) in the neighbourhood of x c and allows one to rationalize the occurrence of instability in terms of electron-density topology and Gibbs energy. The phase/state transitions that TiO 2 (rutile structure), MgO (periclase structure) and Al 2 O 3 (corundum structure) undergo because of pressure and/or temperature are here discussed. An agreement of 3-5% is observed between the theoretical model and experimental pressure/temperature of transformation.

  15. Structure of magnetic field disturbances under development of disruptive instability in the ''Tokamak-6''

    International Nuclear Information System (INIS)

    Merezhkin, V.G.

    1978-01-01

    The structure and dynamics of disturbances of a poloidal field during the development of the breakaway instability in the Tokamak-6 are investigated. The behaviour of the symmetric and dipole field component, and the peculiarities of the structure of screw disturbances in a minor and major breakaways are analyzed. It was established that the structure of screw disturbances in minor breakaways is unchangeable and that the rearrangement in major breakaways is of a discrete nature. The relationship between the symmetric and screw components of disturbances of the poloidal field at the forward front of the disturbance increase was revealed. Data on the increments, scales and structure of screw disturbances, the ratios between the symmetric and screw components of field disturbances, and also on the magnitude of energy losses in typical breakaways are given

  16. Application of Continuous and Structural ARMA modeling for noise analysis of a BWR coupled core and plant instability event

    International Nuclear Information System (INIS)

    Demeshko, M.; Dokhane, A.; Washio, T.; Ferroukhi, H.; Kawahara, Y.; Aguirre, C.

    2015-01-01

    Highlights: • We demonstrate the first application of a novel CSARMA method. • We analyze the instability occurred in a Swiss BWR plant during power ascension. • Benchmarked the results against STP analysis. • The CSARMA results are consistent with the background physics and the STP results. • The instability was caused by disturbances in the pressure control system. - Abstract: This paper presents a first application of a novel Continuous and Structural Autoregressive Moving Average (CSARMA) modeling approach to BWR noise analysis. The CSARMA approach derives a unique representation of the system dynamics by more robust and reliable canonical models as basis for signal analysis in general and for reactor diagnostics in particular. In this paper, a stability event that occurred in a Swiss BWR plant during power ascension phase is analyzed as well as the time periods that preceded and followed the event. Focusing only on qualitative trends at this stage, the obtained results clearly indicate a different dynamical state during the unstable event compared to the two other stable periods. Also, they could be interpreted as pointing out a disturbance in the pressure control system as primary cause for the event. To benchmark these findings, the frequency-domain based signal transmission-path (STP) method is also applied. And with the STP method, we obtained similar relationships as mentioned above. This consistency between both methods can be considered as being a confirmation that the event was caused by a pressure control system disturbance and not induced by the core. Also, it is worth noting that the STP analysis failed to catch the relations among the processes during the stable periods, that were clearly indicated by the CSARMA method, since the last uses more precise models as basis

  17. Satellite radar interferometry for monitoring and early-stage warning of structural instability in archaeological sites

    International Nuclear Information System (INIS)

    Tapete, D; Fanti, R; Casagli, N; Cecchi, R; Petrangeli, P

    2012-01-01

    Satellite interferometric synthetic aperture radar (InSAR) monitoring campaigns were performed on the archaeological heritage of the Roman Forum, Palatino and Oppio Hills in the centre of Rome, Italy, to test the capabilities of persistent scatterer interferometry techniques for the preventive diagnosis of deformation threatening the structural stability of archaeological monuments and buried structures. ERS-1/2 and RADARSAT-1/2 SAR images were processed with the permanent scatterers InSAR (PSInSAR) and SqueeSAR approaches, and the identified measurement points (MP) were radar-interpreted to map the conservation criticalities in relation to the local geohazard factors and active deterioration processes. The multi-temporal reconstruction of past/recent instability events based on the MP deformation time series provided evidences of stabilization for the Domus Tiberiana as a consequence of recent restoration works, as well as of persistent deformation for the Temple of Magna Mater on the Palatino Hill and the structures of the Baths of Trajan on the Oppio Hill. Detailed time series analysis was also exploited to back monitor and understand the nature of the 2010 collapse that occurred close to Nero's Golden House, and to establish an early-stage warning procedure useful to preventively detect potential instability. (paper)

  18. Distinct Mechanisms of Nuclease-Directed DNA-Structure-Induced Genetic Instability in Cancer Genomes.

    Science.gov (United States)

    Zhao, Junhua; Wang, Guliang; Del Mundo, Imee M; McKinney, Jennifer A; Lu, Xiuli; Bacolla, Albino; Boulware, Stephen B; Zhang, Changsheng; Zhang, Haihua; Ren, Pengyu; Freudenreich, Catherine H; Vasquez, Karen M

    2018-01-30

    Sequences with the capacity to adopt alternative DNA structures have been implicated in cancer etiology; however, the mechanisms are unclear. For example, H-DNA-forming sequences within oncogenes have been shown to stimulate genetic instability in mammals. Here, we report that H-DNA-forming sequences are enriched at translocation breakpoints in human cancer genomes, further implicating them in cancer etiology. H-DNA-induced mutations were suppressed in human cells deficient in the nucleotide excision repair nucleases, ERCC1-XPF and XPG, but were stimulated in cells deficient in FEN1, a replication-related endonuclease. Further, we found that these nucleases cleaved H-DNA conformations, and the interactions of modeled H-DNA with ERCC1-XPF, XPG, and FEN1 proteins were explored at the sub-molecular level. The results suggest mechanisms of genetic instability triggered by H-DNA through distinct structure-specific, cleavage-based replication-independent and replication-dependent pathways, providing critical evidence for a role of the DNA structure itself in the etiology of cancer and other human diseases. Copyright © 2018 The Authors. Published by Elsevier Inc. All rights reserved.

  19. Multi-walled carbon nanotube structural instability with/without metal nanoparticles under electron beam irradiation

    Science.gov (United States)

    Khan, Imran; Huang, Shengli; Wu, Chenxu

    2017-12-01

    The structural transformation of multi-walled carbon nanotubes (MWCNT) under electron beam (e-beam) irradiation at room temperature is studied, with respect to a novel passivation effect due to gold nanoparticles (Au NPs). MWCNT structural evolution induced by energetic e-beam irradiation leads to faster shrinkage, as revealed via in situ transmission electron microscopy, while MWCNT surface modification with Au NPs (Au-MWCNT) slows down the shrinkage by impeding the structural evolution process for a prolonged time under the same irradiation conditions. The new relationship between MWCNT and Au-MWCNT shrinking radii and irradiation time illustrates that the MWCNT shrinkage rate is faster than either theoretical predictions or the same process in Au-MWCNTs. As compared with the outer surface energy (positive curvature), the inner surface energy (negative curvature) of the MWCNT contributes more to the athermal evaporation of tube wall atoms, leading to structural instability and shrinkage under e-beam irradiation. Conversely, Au NPs possess only outer surface energy (positive curvature) compared with the MWCNT. Their presence on MWCNT surfaces retards the dynamics of MWCNT structural evolution by slowing down the evaporation process of carbon atoms, thus restricting Au-MWCNT shrinkage. Au NP interaction and growth evolves athermally on MWCNT surfaces, exhibits increase in their size, and indicates the association of this mechanism with the coalescence induced by e-beam activated electronic excitations. Despite their growth, Au NPs show extreme structural stability, and remain crystalline under prolonged irradiation. It is proposed that the surface energy of MWCNTs and Au NPs, together with e-beam activated soft modes or lattice instability effects, predominantly govern all the above varieties of structural evolution.

  20. Non-linear hydrodynamic instability and turbulence in eccentric astrophysical discs with vertical structure

    Science.gov (United States)

    Wienkers, A. F.; Ogilvie, G. I.

    2018-04-01

    Non-linear evolution of the parametric instability of inertial waves inherent to eccentric discs is studied by way of a new local numerical model. Mode coupling of tidal deformation with the disc eccentricity is known to produce exponentially growing eccentricities at certain mean-motion resonances. However, the details of an efficient saturation mechanism balancing this growth still are not fully understood. This paper develops a local numerical model for an eccentric quasi-axisymmetric shearing box which generalises the often-used cartesian shearing box model. The numerical method is an overall second order well-balanced finite volume method which maintains the stratified and oscillatory steady-state solution by construction. This implementation is employed to study the non-linear outcome of the parametric instability in eccentric discs with vertical structure. Stratification is found to constrain the perturbation energy near the mid-plane and localise the effective region of inertial wave breaking that sources turbulence. A saturated marginally sonic turbulent state results from the non-linear breaking of inertial waves and is subsequently unstable to large-scale axisymmetric zonal flow structures. This resulting limit-cycle behaviour reduces access to the eccentric energy source and prevents substantial transport of angular momentum radially through the disc. Still, the saturation of this parametric instability of inertial waves is shown to damp eccentricity on a time-scale of a thousand orbital periods. It may thus be a promising mechanism for intermittently regaining balance with the exponential growth of eccentricity from the eccentric Lindblad resonances and may also help explain the occurrence of "bursty" dynamics such as the superhump phenomenon.

  1. Nonlinear vortex structures and Rayleigh instability condition in shear flow plasmas

    International Nuclear Information System (INIS)

    Haque, Q.; Saleem, H.; Mirza, A.M.

    2009-01-01

    Full text: It is shown that the shear flow produced by externally applied electric field can unstable the drift waves. Due to shear flow, the Rayleigh instability condition is modified, which is obtained for both electron-ion and electron-positron-ion plasmas. These shear flow driven drift waves can be responsible for large amplitude electrostatic fluctuations in tokamak edges. In the nonlinear regime, the stationary structures may appear in electron-positron-ion plasmas similar to electron-ion plasmas. The nonlinear vortex structures like counter rotating dipole vortices and vortex chains can be formed with the aid of special type of shear flows. The positrons can be used as a probe in laboratory plasmas, which make it a multi-component plasma. The presence of positrons in electron-ion plasma system can affect the speed and amplitude of the nonlinear vortex structures. This investigation can have application in both laboratory and astrophysical plasmas. (author)

  2. The origin and structure of streak-like instabilities in laminar boundary layer flames

    Science.gov (United States)

    Gollner, Michael; Miller, Colin; Tang, Wei; Finney, Mark

    2017-11-01

    Streamwise streaks are consistently observed in wildland fires, at the base of pool fires, and in other heated flows within a boundary layer. This study examines both the origin of these structures and their role in influencing some of the macroscopic properties of the flow. Streaks were reproduced and characterized via experiments on stationary heated strips and liquid and gas-fueled burners in laminar boundary layer flows, providing a framework to develop theory based on both observed and measured physical phenomena. The incoming boundary layer was established as the controlling mechanism in forming streaks, which are generated by pre-existing coherent structures, while the amplification of streaks was determined to be compatible with quadratic growth of Rayleigh-Taylor Instabilities, providing credence to the idea that the downstream growth of streaks is strongly tied to buoyancy. These local instabilities were also found to affect macroscopic properties of the flow, including heat transfer to the surface, indicating that a two-dimensional assumption may fail to adequately describe heat and mass transfer during flame spread and other reacting boundary layer flows. This work was supported by NSF (CBET-1554026) and the USDA-FS (13-CS-11221637-124).

  3. Carpal instability

    International Nuclear Information System (INIS)

    Schmitt, R.; Froehner, S.; Coblenz, G.; Christopoulos, G.

    2006-01-01

    This review addresses the pathoanatomical basics as well as the clinical and radiological presentation of instability patterns of the wrist. Carpal instability mostly follows an injury; however, other diseases, like CPPD arthropathy, can be associated. Instability occurs either if the carpus is unable to sustain physiologic loads (''dyskinetics'') or suffers from abnormal motion of its bones during movement (''dyskinematics''). In the classification of carpal instability, dissociative subcategories (located within proximal carpal row) are differentiated from non-dissociative subcategories (present between the carpal rows) and combined patterns. It is essential to note that the unstable wrist initially does not cause relevant signs in standard radiograms, therefore being ''occult'' for the radiologic assessment. This paper emphasizes the high utility of kinematographic studies, contrast-enhanced magnetic resonance imaging (MRI) and MR arthrography for detecting these predynamic and dynamic instability stages. Later in the natural history of carpal instability, static malalignment of the wrist and osteoarthritis will develop, both being associated with significant morbidity and disability. To prevent individual and socio-economic implications, the handsurgeon or orthopedist, as well as the radiologist, is challenged for early and precise diagnosis. (orig.)

  4. Instability Mechanisms of Water-in-Oil Nanoemulsions with Phospholipids: Temporal and Morphological Structures.

    Science.gov (United States)

    Sommerling, Jan-Hendrik; de Matos, Maria B C; Hildebrandt, Ellen; Dessy, Alberto; Kok, Robbert Jan; Nirschl, Hermann; Leneweit, Gero

    2018-01-16

    Many food preparations, pharmaceuticals, and cosmetics use water-in-oil (W/O) emulsions stabilized by phospholipids. Moreover, recent technological developments try to produce liposomes or lipid coated capsules from W/O emulsions, but are faced with colloidal instabilities. To explore these instability mechanisms, emulsification by sonication was applied in three cycles, and the sample stability was studied for 3 h after each cycle. Clearly identifiable temporal structures of instability provide evidence about the emulsion morphology: an initial regime of about 10 min is shown to be governed by coalescence after which Ostwald ripening dominates. Transport via molecular diffusion in Ostwald ripening is commonly based on the mutual solubility of the two phases and is therefore prohibited in emulsions composed of immiscible phases. However, in the case of water in oil emulsified by phospholipids, these form water-loaded reverse micelles in oil, which enable Ostwald ripening despite the low solubility of water in oil, as is shown for squalene. As is proved for the phospholipid dipalmitoylphosphatidylcholine (DPPC), concentrations below the critical aggregation concentration (CAC) form monolayers at the interfaces and smaller droplet sizes. In contrast, phospholipid concentrations above the CAC create complex multilayers at the interface with larger droplet sizes. The key factors for stable W/O emulsions in classical or innovative applications are first, the minimization of the phospholipids' capacity to form reversed micelles, and second, the adaption of the initial phospholipid concentration to the water content to enable an optimized coverage of phospholipids at the interfaces for the intended drop size.

  5. Parametric instability producing broad symmetrical structure in the spectrum of ionospheric heating-induced radiation

    International Nuclear Information System (INIS)

    Kuo, S.P.

    1997-01-01

    A four-wave interaction process in which an O-mode electromagnetic pump decays parametrically into a lower hybrid decay mode and two-electron Bernstein sidebands is analyzed. It is shown that the instability can be excited in a spatial region near the electron Bernstein/upper hybrid double resonance and in a narrow pump frequency range slightly below the third harmonic electron cyclotron resonance. The two electron Bernstein sidebands have about the same intensity and thus, produce Broad Symmetrical Structure (BSS) in the emission spectrum after being converted into electromagnetic radiation by scattering off background field-aligned density irregularities. The results also show that the size of the instability zone becomes very small as the pump frequency operates near a cyclotron harmonic higher than the third. Thus, the converted emission will be too weak to be detected. This explains why the BSS feature in the spectrum of stimulated electromagnetic emissions (SEEs) has only been observed in the third harmonic case. copyright 1997 American Institute of Physics

  6. Modulational instability and associated rogue structures of slow magnetosonic wave in Hall magnetohydrodynamic plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Panwar, Anuraj; Ryu, Chang-Mo [Department of Physics, POSTECH, Hyoja-Dong San 31, KyungBuk, Pohang 790-784 (Korea, Republic of)

    2014-06-15

    The modulational instability and associated rogue structures of a slow magnetosonic wave are investigated for a Hall magnetohydrodynamic plasma. Nonlinear Schrodinger equation is obtained by using the multiple scale method, which shows a modulationally unstable slow magnetosonic mode evolving into bright wavepackets. The dispersive effects induced by the Hall electron current increase with the increase in plasma β and become weaker as the angle of propagation increases. The growth rate of the modulational instability also increases with the increase in plasma β. The growth rate is greatest for the parallel propagation and drops to zero for perpendicular propagation. The envelope wavepacket of a slow magnetosonic is widened with less oscillations as plasma β increases. But the wavepacket becomes slightly narrower and more oscillatory as the angle of propagation increases. Further a non-stationary envelope solution of the Peregrine soliton is analyzed for rogue waves. The Peregrine soliton contracts temporally and expands spatially with increase in plasma β. However, the width of a slow magnetosonic Peregrine soliton decreases both temporally and spatially with increase of the propagation angle.

  7. Antiferromagnetism, structural instability and frustration in intermetallic AFe4X2 systems

    Science.gov (United States)

    Rosner, Helge; Bergmann, Christoph; Weber, Katharina; Kraft, Inga; Mufti, N.; Klauss, Hans-Henning; Dellmann, T.; Woike, T.; Geibel, Christoph

    2013-03-01

    Magnetic systems with reduced dimensionality or frustration attract strong interest because these features lead to an increase of quantum fluctuations and often result in unusual properties. Here, we present a detailed study of the magnetic, thermodynamic, and structural properties of the intermetallic AFe4X2 compounds (A=Sc,Y,Lu,Zr; X=Si,Ge) crystallizing in the ZrFe4Si2 structure type. Our results evidence that these compounds cover the whole regime from frustrated AFM order up to an AFM quantum critical point. Susceptibility χ(T), specific heat, resistivity, and T-dependent XRD measurements were performed on polycrystalline samples. In all compounds we observed a Curie-Weiss behavior in χ(T) at high T indicating a paramagnetic moment of about 3μB/Fe. Magnetic and structural transitions as previously reported for YFe4Ge2 occur in all compounds with trivalent A. However, transition temperatures, nature of the transition as well as the relation between structural and magnetic transitions change significantly with the A element. Low TN's and large θCW /TN ratios confirm the relevance of frustration. The results are analyzed and discussed with respect to electronic, structural and magnetic instabilities applying DFT calculations. Financial support from the DFG (GRK 1621) is acknowledged

  8. Experimental research on the structural instability mechanism and the effect of multi-echelon support of deep roadways in a kilometre-deep well.

    Directory of Open Access Journals (Sweden)

    Rui Peng

    Full Text Available We study the structural instability mechanism and effect of a multi-echelon support in very-deep roadways. We conduct a scale model test for analysing the structural failure mechanism and the effect of multi-echelon support of roadways under high horizontal stress. Mechanical bearing structures are classified according to their secondary stress distribution and the strength degradation of the surrounding rock after roadway excavation. A new method is proposed by partitioning the mechanical bearing structure of the surrounding rock into weak, key and main coupling bearing stratums. In the surrounding rock, the main bearing stratum is the plastic reshaping and flowing area. The weak bearing stratum is the peeling layer or the caving part. And the key bearing stratum is the shearing and yielding area. The structural fracture mechanism of roadways is considered in analysing the bearing structure instability of the surrounding rock, and multi-echelon support that considers the structural characteristics of roadway bearings is proposed. Results of the experimental study indicate that horizontal pressure seriously influences the stability of the surrounding rock, as indicated by extension of the weak bearing area and the transfer of the main and key bearing zones. The falling roof, rib spalling, and floor heave indicate the decline of the bearing capacity of surrounding rock, thereby causing roadway structural instability. Multi-echelon support is proposed according to the mechanical bearing structure of the surrounding rock without support. The redesigned support can reduce the scope of the weak bearing area and limit the transfer of the main and key bearing areas. Consequently, kilometre-deep roadway disasters, such as wedge roof caving, floor heave, and rib spalling, can be avoided to a certain degree, and plastic flow in the surrounding rock is relieved. The adverse effect of horizontal stress on the vault, spandrel and arch foot decreases. The

  9. Study of tertiary creep instability in several elevated-temperature structural materials

    International Nuclear Information System (INIS)

    Booker, M.K.; Sikka, V.K.

    1978-01-01

    Data for a number of common elevated temperature structural materials have been analyzed to yield mathematical predictions for the time and strain to tertiary creep at various rupture lives and temperatures. Materials examined include types 304 and 316 stainless steel, 2 1/4 Cr-1 Mo steel, alloy 800H, alloy 718, Hastelloy alloy X, and ERNiCr--3 weld metal. Data were typically examined over a range of creep temperatures for rupture lives ranging from less than 100 to greater than 10,000 hours. Within a given material, trends in these quantities can be consistently described, but it is difficult to directly relate the onset of tertiary creep to failure-inducing instabilities. A series of discontinued tests for alloy 718 at 649 and 620 0 C showed that the material fails by intergranular cracking but that no significant intergranular cracking occurs until well after the onset of tertiary creep

  10. Ion Streaming Instabilities in Pair Ion Plasma and Localized Structure with Non-Thermal Electrons

    Science.gov (United States)

    Nasir Khattak, M.; Mushtaq, A.; Qamar, A.

    2015-12-01

    Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A qausi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted.

  11. Ion streaming instabilities in pair ion plasma and localized structure with non-thermal electrons

    Energy Technology Data Exchange (ETDEWEB)

    Khattak, M. Nasir; Qamar, A., E-mail: mnnasirphysics@gmail.com [Department of Physics, University of Peshawar (Pakistan); Mushtaq, A. [Department of Physics, Abdul Wali Khan University Mardan, National Center for Physics, Mardan (Pakistan)

    2015-12-15

    Pair ion plasma with a fraction of non-thermal electrons is considered. We investigate the effects of the streaming motion of ions on linear and nonlinear properties of unmagnetized, collisionless plasma by using the fluid model. A dispersion relation is derived, and the growth rate of streaming instabilities with effect of streaming motion of ions and non-thermal electrons is calculated. A quasi-potential approach is adopted to study the characteristics of ion acoustic solitons. An energy integral equation involving Sagdeev potential is derived during this process. The presence of the streaming term in the energy integral equation affects the structure of the solitary waves significantly along with non-thermal electrons. Possible application of the work to the space and laboratory plasmas are highlighted. (author)

  12. Analytical and numerical study of MHD instabilities development in magnetized accretion-ejection structures

    International Nuclear Information System (INIS)

    Kersale, Evy

    2000-01-01

    The first part of this work proposes a new version of the mathematical formalism used to describe pressure-driven instabilities in magnetized accretion-ejection structures. Such processes, occurring in magnetically confined plasmas, pose very stringent limits to thermonuclear fusion devices but their influence in astrophysical objects has rarely been considered. In a framework which eliminates fast magnetosonic waves one develops a system of equations allowing us to follow both ballooning and interchange modes. An application of this result to a cylindrical jet being subject to solid rotation shows that the inner parts of such structures are destabilized by magnetic shear. Furthermore, while clarifying somewhat previous studies, one finds that jets confined by a dominant toroidal magnetic field are generically unstable with respect to interchange modes. Moreover, one has written a numerical code to solve the MHD partial differential equations. Starting with a basic algorithm, one has assessed the effects of the geometry, boundary conditions and artificial dissipation on numerical computation. The code has been tested by solving classical hydrodynamic and MHD Riemann problems. A new mechanism of ultra high energy cosmic ray production in gamma-ray bursts composes the last part of this work. In these objects, particles are accelerated up to energies of the order of 10 21 eV, by means of relativistic Alfven perturbations crossings. A stream instability involving a highly relativistic shell of plasma, the fireball, and baryons going through it produces such Alfven fronts. Then, Brillouin-like backscattering processes redistribute the available energy between the forward and backward Alfven waves and the magnetosonic ones. (author) [fr

  13. Mirror structures above and below the linear instability threshold: Cluster observations, fluid model and hybrid simulations

    Directory of Open Access Journals (Sweden)

    V. Génot

    2009-02-01

    Full Text Available Using 5 years of Cluster data, we present a detailed statistical analysis of magnetic fluctuations associated with mirror structures in the magnetosheath. We especially focus on the shape of these fluctuations which, in addition to quasi-sinusoidal forms, also display deep holes and high peaks. The occurrence frequency and the most probable location of the various types of structures is discussed, together with their relation to local plasma parameters. While these properties have previously been correlated to the β of the plasma, we emphasize here the influence of the distance to the linear mirror instability threshold. This enables us to interpret the observations of mirror structures in a stable plasma in terms of bistability and subcritical bifurcation. The data analysis is supplemented by the prediction of a quasi-static anisotropic MHD model and hybrid numerical simulations in an expanding box aimed at mimicking the magnetosheath plasma. This leads us to suggest a scenario for the formation and evolution of mirror structures.

  14. Structural cause of dysphagia detected during videofluoroscopic swallow study

    OpenAIRE

    Toh Yoon, Ezekiel Wong; Kabuto, Syu

    2017-01-01

    Key Clinical Message Dysphagia can be caused by many different underlying conditions. The assessment and management of dysphagia depend on each individual patient, often requiring a multidisciplinary approach. Structural cause of dysphagia can be dealt with using endoscopic interventions before the patient's general status deteriorates.

  15. Spin-orbit coupling, electron transport and pairing instabilities in two-dimensional square structures

    Energy Technology Data Exchange (ETDEWEB)

    Kocharian, Armen N. [Department of Physics, California State University, Los Angeles, CA 90032 (United States); Fernando, Gayanath W.; Fang, Kun [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Palandage, Kalum [Department of Physics, Trinity College, Hartford, Connecticut 06106 (United States); Balatsky, Alexander V. [AlbaNova University Center Nordita, SE-106 91 Stockholm (Sweden)

    2016-05-15

    Rashba spin-orbit effects and electron correlations in the two-dimensional cylindrical lattices of square geometries are assessed using mesoscopic two-, three- and four-leg ladder structures. Here the electron transport properties are systematically calculated by including the spin-orbit coupling in tight binding and Hubbard models threaded by a magnetic flux. These results highlight important aspects of possible symmetry breaking mechanisms in square ladder geometries driven by the combined effect of a magnetic gauge field spin-orbit interaction and temperature. The observed persistent current, spin and charge polarizations in the presence of spin-orbit coupling are driven by separation of electron and hole charges and opposite spins in real-space. The modeled spin-flip processes on the pairing mechanism induced by the spin-orbit coupling in assembled nanostructures (as arrays of clusters) engineered in various two-dimensional multi-leg structures provide an ideal playground for understanding spatial charge and spin density inhomogeneities leading to electron pairing and spontaneous phase separation instabilities in unconventional superconductors. Such studies also fall under the scope of current challenging problems in superconductivity and magnetism, topological insulators and spin dependent transport associated with numerous interfaces and heterostructures.

  16. Spin-orbit coupling, electron transport and pairing instabilities in two-dimensional square structures

    Directory of Open Access Journals (Sweden)

    Armen N. Kocharian

    2016-05-01

    Full Text Available Rashba spin-orbit effects and electron correlations in the two-dimensional cylindrical lattices of square geometries are assessed using mesoscopic two-, three- and four-leg ladder structures. Here the electron transport properties are systematically calculated by including the spin-orbit coupling in tight binding and Hubbard models threaded by a magnetic flux. These results highlight important aspects of possible symmetry breaking mechanisms in square ladder geometries driven by the combined effect of a magnetic gauge field spin-orbit interaction and temperature. The observed persistent current, spin and charge polarizations in the presence of spin-orbit coupling are driven by separation of electron and hole charges and opposite spins in real-space. The modeled spin-flip processes on the pairing mechanism induced by the spin-orbit coupling in assembled nanostructures (as arrays of clusters engineered in various two-dimensional multi-leg structures provide an ideal playground for understanding spatial charge and spin density inhomogeneities leading to electron pairing and spontaneous phase separation instabilities in unconventional superconductors. Such studies also fall under the scope of current challenging problems in superconductivity and magnetism, topological insulators and spin dependent transport associated with numerous interfaces and heterostructures.

  17. Sites of instability in the human TCF3 (E2A) gene adopt G-quadruplex DNA structures in vitro

    Science.gov (United States)

    Williams, Jonathan D.; Fleetwood, Sara; Berroyer, Alexandra; Kim, Nayun; Larson, Erik D.

    2015-01-01

    The formation of highly stable four-stranded DNA, called G-quadruplex (G4), promotes site-specific genome instability. G4 DNA structures fold from repetitive guanine sequences, and increasing experimental evidence connects G4 sequence motifs with specific gene rearrangements. The human transcription factor 3 (TCF3) gene (also termed E2A) is subject to genetic instability associated with severe disease, most notably a common translocation event t(1;19) associated with acute lymphoblastic leukemia. The sites of instability in TCF3 are not randomly distributed, but focused to certain sequences. We asked if G4 DNA formation could explain why TCF3 is prone to recombination and mutagenesis. Here we demonstrate that sequences surrounding the major t(1;19) break site and a region associated with copy number variations both contain G4 sequence motifs. The motifs identified readily adopt G4 DNA structures that are stable enough to interfere with DNA synthesis in physiological salt conditions in vitro. When introduced into the yeast genome, TCF3 G4 motifs promoted gross chromosomal rearrangements in a transcription-dependent manner. Our results provide a molecular rationale for the site-specific instability of human TCF3, suggesting that G4 DNA structures contribute to oncogenic DNA breaks and recombination. PMID:26029241

  18. Novel magnetic resonance imaging evaluation for valgus instability of the knee caused by medial collateral ligament injury

    International Nuclear Information System (INIS)

    Ikuma, Hisanori; Abe, Nobuhiro; Furumatsu, Takayuki; Uchida, Youichiro; Fujiwara, Kazuo; Nishida, Keiichiro; Ozaki, Toshifumi

    2008-01-01

    Instability of the knee after the medial collateral ligament (MCL) injury is usually assessed with the manual valgus stress test, even though, in recent years, it has become possible to apply magnetic resonance imaging (MRI) to the assessment of the damage of the ligament. The valgus instability of 24 patients (12 isolated injuries and 12 multiple ligament injuries) who suffered MCL injury between 1993 and 1998 was evaluated with the Hughston and Eilers classification, which involves radiographic assessment under manual valgus stress to the injured knees. We developed a novel system for classifying the degree of injury to the MCL by calculating the percentage of injured area based on MRI and investigated the relationship between this novel MRI classification and the magnitude of valgus instability by the Hughston and Eilers classification. There was a significant correlation between the 2 classifications (p=0.0006). On the other hand, the results using other MRI based classification systems, such as the Mink and Deutsch classification and the Petermann classification, were not correlated with the findings by the Hughston and Eilers classification in these cases (p>0.05). Since MRI is capable of assessing the injured ligament in clinical practice, this novel classification system would be useful for evaluating the stability of the knee and choosing an appropriate treatment following MCL injury. (author)

  19. Instabilities in inhomogeneous plasma

    International Nuclear Information System (INIS)

    Mikhailovsky, A.B.

    1983-01-01

    The plasma inhomogeneity across the magnetic field causes a wide class of instabilities which are called instabilities of an inhomogeneous plasma or gradient instabilities. The instabilities that can be studied in the approximation of a magnetic field with parallel straight field lines are treated first, followed by a discussion of the influence of shear on these instabilities. The instabilities of a weakly inhomogeneous plasma with the Maxwellian velocity distribution of particles caused by the density and temperature gradients are often called drift instabilities, and the corresponding types of perturbations are the drift waves. An elementary theory of drift instabilities is presented, based on the simplest equations of motion of particles in the field of low-frequency and long-wavelength perturbations. Following that is a more complete theory of inhomogeneous collisionless plasma instabilities which uses the permittivity tensor and, in the case of electrostatic perturbations, the scalar of permittivity. The results are used to study the instabilities of a strongly inhomogeneous plasma. The instabilities of a plasma in crossed fields are discussed and the electromagnetic instabilities of plasma with finite and high pressure are described. (Auth.)

  20. Focal ischaemia caused by instability of cerebrovascular tone during attacks of hemiplegic migraine. A regional cerebral blood flow study

    DEFF Research Database (Denmark)

    Friberg, L; Olsen, T S; Roland, P E

    1987-01-01

    During the course of hemiplegic migraine in 3 patients, changes in regional cerebral blood flow (rCBF) were recorded by the intracarotid 133Xe method and a 254 multidetector camera covering one hemisphere. The rCBF measurements were performed in conjunction with cerebral angiography. During...... the patients developed transient motor and/or sensory deficits and subsequently severe headache. No signs of arterial occlusion were found. In the over and underperfused regions blood flow fluctuated rapidly because of instability of cerebrovascular tone, defined as transient constriction of the smallest...

  1. Stream instability countermeasures applied at Kansas Department of Transportation highway structures.

    Science.gov (United States)

    2008-11-01

    This project considered stream instability countermeasures used by the Kansas Department of Transportation (KDOT) to protect the highway infrastructure at stream crossings from changes due to the dynamic nature of streams. Site visits were made to 13...

  2. Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

    International Nuclear Information System (INIS)

    Ivanov, Vladimir V.

    2016-01-01

    Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications, but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics, magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution 20 MG, suggested in micropinches, Cotton-Mouton and cutoff diagnostics will be applied. A picosecond optical Kerr shutter will be tested to increase a sensitivity of UV methods for application at multi-MA Z pinches. The proposal is based on the experimental capability of NTF. The Zebra generator produces 1-1.7 MA Z-pinches with electron plasma density of 10"2"0-10"2"1cm"-"3, electron temperature of 0.5-1 keV, and magnetic fields >10 MG. The Leopard laser was upgraded to energy of 90-J at 0.8 ns. This regime will be used for laser initiation

  3. Study of the internal structure, instabilities, and magnetic fields in the dense Z-pinch

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Vladimir V. [Univ. of Nevada, Reno, NV (United States)

    2016-08-17

    Z-pinches are sources of hot dense plasma which generates powerful x-ray bursts and can been applied to various areas of high-energy-density physics (HEDP). The 26-MA Z machine is at the forefront of many of these applications, but important aspects of HEDP have been studied on generators at the 1 MA current level. Recent development of laser diagnostics and upgrade of the Leopard laser at Nevada Terawatt Facility (NTF) give new opportunities for the dense Z-pinch study. The goal of this project is the investigation of the internal structure of the stagnated Z pinch including sub-mm and micron-scale instabilities, plasma dynamics, magnetic fields, and hot spots formation and initiation. New plasma diagnostics will be developed for this project. A 3D structure and instabilities of the pinch will be compared with 3D MHD and spectroscopic modeling and theoretical analysis. The structure and dynamics of stagnated Z pinches has been studied with x-ray self-radiation diagnostics which derive a temperature map of the pinch with a spatial resolution of 70-150 µm. The regular laser diagnostics at 532 nm does not penetrate in the dense pinch due to strong absorption and refraction in trailing plasma. Recent experiments at NTF showed that shadowgraphy at the UV wavelength of 266 nm unfolds a fine structure of the stagnated Z-pinch with unprecedented detail. We propose to develop laser UV diagnostics for Z pinches with a spatial resolution <5 μm to study the small-scale plasma structures, implement two-frame shadowgraphy/interferometry, and develop methods for investigation of strong magnetic fields. New diagnostics will help to understand better basic physical processes in Z pinches. A 3D internal structure of the pinch and characteristic instabilities will be studied in wire arrays with different configurations and compared with 3D MHD simulations and analytical models. Mechanisms of “enhanced heating” of Z-pinch plasma will be studied. Fast dynamics of stagnated

  4. Thermo-kinetic mechanisms for grain boundary structure multiplicity, thermal instability and defect interactions

    International Nuclear Information System (INIS)

    Burbery, N.J.; Das, R.; Ferguson, W.G.

    2016-01-01

    Grain boundaries (GBs) provide a source and/or a sink for crystal defects and store elastic energy due to the non-uniform atomic bonding structure of the GB core. GB structures are thermodynamically driven to transition to the lowest energy configuration possible; however to date there has been little evidence to explain why specific GB structures have a low energy state. Furthermore, there is little quantitative demonstration of the significance of physical and GB structure characteristics on the GB energy, thermal stability, and the effect of temporary local GB structure transformations on defect interactions. This paper evaluates the defect interactions and structure stability of multiple Σ5(310) GB structures in bi-crystals of pure aluminium, and systematically investigates the features at 0 K to characterise multiple metastable structures. Structure stability is evaluated by utilising unstable vacancy defects to initiate GB transformations, and using nudged elastic band simulations to quantify this with the activation energy. The emission of stable vacancy defects from the ‘stable’ and metastable grain boundaries is also evaluated in the same manner. A detailed analysis of dislocation nucleation at the atomistic scale demonstrates that local transformations of GB structure between stable and metastable intermediates can provide a mechanism to accommodate the generation of crystal defects. Kinetic (time-dependent) effects that compete with energetic driving forces for structural transformations of GBs are shown to cause a significant effect on the activation properties that may exceed the influence of GB potential energy. The results demonstrate that GB structural multiplicity can be associated with the generation and absorption of dislocations and vacancies. This paper demonstrates the suitability of atomistic simulations coupled with nudged elastic band simulations to evaluate fundamental thermodynamic properties of pure FCC metals. Overall, this paper

  5. Thermo-kinetic mechanisms for grain boundary structure multiplicity, thermal instability and defect interactions

    Energy Technology Data Exchange (ETDEWEB)

    Burbery, N.J. [Department of Mechanical Engineering, University of Auckland, Auckland 1010 (New Zealand); Das, R., E-mail: r.das@auckland.ac.nz [Department of Mechanical Engineering, University of Auckland, Auckland 1010 (New Zealand); Ferguson, W.G. [Department of Chemical and Materials Engineering, University of Auckland, Auckland 1010 (New Zealand)

    2016-08-15

    Grain boundaries (GBs) provide a source and/or a sink for crystal defects and store elastic energy due to the non-uniform atomic bonding structure of the GB core. GB structures are thermodynamically driven to transition to the lowest energy configuration possible; however to date there has been little evidence to explain why specific GB structures have a low energy state. Furthermore, there is little quantitative demonstration of the significance of physical and GB structure characteristics on the GB energy, thermal stability, and the effect of temporary local GB structure transformations on defect interactions. This paper evaluates the defect interactions and structure stability of multiple Σ5(310) GB structures in bi-crystals of pure aluminium, and systematically investigates the features at 0 K to characterise multiple metastable structures. Structure stability is evaluated by utilising unstable vacancy defects to initiate GB transformations, and using nudged elastic band simulations to quantify this with the activation energy. The emission of stable vacancy defects from the ‘stable’ and metastable grain boundaries is also evaluated in the same manner. A detailed analysis of dislocation nucleation at the atomistic scale demonstrates that local transformations of GB structure between stable and metastable intermediates can provide a mechanism to accommodate the generation of crystal defects. Kinetic (time-dependent) effects that compete with energetic driving forces for structural transformations of GBs are shown to cause a significant effect on the activation properties that may exceed the influence of GB potential energy. The results demonstrate that GB structural multiplicity can be associated with the generation and absorption of dislocations and vacancies. This paper demonstrates the suitability of atomistic simulations coupled with nudged elastic band simulations to evaluate fundamental thermodynamic properties of pure FCC metals. Overall, this paper

  6. Isotope separation of uranium by laser: tuning and frequency instability

    International Nuclear Information System (INIS)

    Broglia, M.; Massimi, M.; Spoglia, U.; Zampetti, P.

    1983-01-01

    Intensity measurements of laser induced fluorescence in an uranium atomic beam are affected by the axial mode structure of the commercial pulsed dye laser used and by its strong frequency instability. Qualitative and quantitative evaluations on the possible causes of frequency instability are reported

  7. Numerical MHD study for plasmoid instability in uniform resistivity

    Science.gov (United States)

    Shimizu, Tohru; Kondoh, Koji; Zenitani, Seiji

    2017-11-01

    The plasmoid instability (PI) caused in uniform resistivity is numerically studied with a MHD numerical code of HLLD scheme. It is shown that the PI observed in numerical studies may often include numerical (non-physical) tearing instability caused by the numerical dissipations. By increasing the numerical resolutions, the numerical tearing instability gradually disappears and the physical tearing instability remains. Hence, the convergence of the numerical results is observed. Note that the reconnection rate observed in the numerical tearing instability can be higher than that of the physical tearing instability. On the other hand, regardless of the numerical and physical tearing instabilities, the tearing instability can be classified into symmetric and asymmetric tearing instability. The symmetric tearing instability tends to occur when the thinning of current sheet is stopped by the physical or numerical dissipations, often resulting in the drastic changes in plasmoid chain's structure and its activity. In this paper, by eliminating the numerical tearing instability, we could not specify the critical Lundquist number Sc beyond which PI is fully developed. It suggests that Sc does not exist, at least around S = 105.

  8. Characterizing the turbulent porosity of stellar wind structure generated by the line-deshadowing instability

    Science.gov (United States)

    Owocki, Stanley P.; Sundqvist, Jon O.

    2018-03-01

    We analyse recent 2D simulations of the non-linear evolution of the line-deshadowing instability (LDI) in hot-star winds, to quantify how the associated highly clumped density structure can lead to a `turbulent porosity' reduction in continuum absorption and/or scattering. The basic method is to examine the statistical variations of mass column as a function of path length, and fit these to analytic forms that lead to simple statistical scalings for the associated mean extinction. A key result is that one can characterize porosity effects on continuum transport in terms of a single `turbulent porosity length', found here to scale as H ≈ (fcl - 1)a, where fcl ≡ 〈ρ2〉/〈ρ〉2 is the clumping factor in density ρ, and a is the density autocorrelation length. For continuum absorption or scattering in an optically thick layer, we find the associated effective reduction in opacity scales as ˜ 1/√{1+τ_H}, where τH ≡ κρH is the local optical thickness of this porosity length. For these LDI simulations, the inferred porosity lengths are small, only about a couple per cent of the stellar radius, H ≈ 0.02R*. For continuum processes like bound-free absorption of X-rays that are only marginally optically thick throughout the full stellar wind, this implies τH ≪ 1, and thus that LDI-generated porosity should have little effect on X-ray transport in such winds. The formalism developed here could however be important for understanding the porous regulation of continuum-driven, super-Eddington outflows from luminous blue variables.

  9. Overexpression of eIF-5A2 in mice causes accelerated organismal aging by increasing chromosome instability

    Directory of Open Access Journals (Sweden)

    Chen Leilei

    2011-05-01

    Full Text Available Abstract Background Amplification of 3q26 is one of the most frequent genetic alterations in many human malignancies. Recently, we isolated a novel oncogene eIF-5A2 within the 3q26 region. Functional study has demonstrated the oncogenic role of eIF-5A2 in the initiation and progression of human cancers. In the present study, we aim to investigate the physiological and pathological effect of eIF-5A2 in an eIF-5A2 transgenic mouse model. Methods An eIF-5A2 transgenic mouse model was generated using human eIF-5A2 cDNA. The eIF-5A2 transgenic mice were characterized by histological and immunohistochemistry analyses. The aging phenotypes were further characterized by wound healing, bone X-ray imaging and calcification analysis. Mouse embryo fibroblasts (MEF were isolated to further investigate molecular mechanism of eIF-5A2 in aging. Results Instead of resulting in spontaneous tumor formation, overexpression of eIF-5A2 accelerated the aging process in adult transgenic mice. This included decreased growth rate and body weight, shortened life span, kyphosis, osteoporosis, delay of wound healing and ossification. Investigation of the correlation between cellular senescence and aging showed that cellular senescence is not required for the aging phenotypes in eIF-5A2 mice. Interestingly, we found that activation of eIF-5A2 repressed p19 level and therefore destabilized p53 in transgenic mouse embryo fibroblast (MEF cells. This subsequently allowed for the accumulation of chromosomal instability, such as errors in cell dividing during metaphase and anaphase. Additionally, a significantly increase in number of aneuploidy cells (p Conclusion These observations suggest that eIF-5A2 mouse models could accelerate organismal aging by increasing chromosome instability.

  10. Ocean acidification causes structural deformities in juvenile coral skeletons.

    Science.gov (United States)

    Foster, Taryn; Falter, James L; McCulloch, Malcolm T; Clode, Peta L

    2016-02-01

    Rising atmospheric CO2 is causing the oceans to both warm and acidify, which could reduce the calcification rates of corals globally. Successful coral recruitment and high rates of juvenile calcification are critical to the replenishment and ultimate viability of coral reef ecosystems. Although elevated Pco2 (partial pressure of CO2) has been shown to reduce the skeletal weight of coral recruits, the structural changes caused by acidification during initial skeletal deposition are unknown. We show, using high-resolution three-dimensional x-ray microscopy, that ocean acidification (Pco2 ~900 μatm, pH ~7.7) not only causes reduced overall mineral deposition but also a deformed and porous skeletal structure in newly settled coral recruits. In contrast, elevated temperature (+3°C) had little effect on skeletal formation except to partially mitigate the effects of elevated Pco2. The striking structural deformities we observed show that new recruits are at significant risk, being unable to effectively build their skeletons in the Pco2 conditions predicted to occur for open ocean surface waters under a "business-as-usual" emissions scenario [RCP (representative concentration pathway) 8.5] by the year 2100.

  11. Instability Mechanisms of Water-in-Oil Nanoemulsions with Phospholipids : Temporal and Morphological Structures

    NARCIS (Netherlands)

    Sommerling, Jan-Hendrik; Carreira de Matos, Maria; Hildebrandt, Ellen; Dessy, Alberto; Kok, Robbert Jan; Nirschl, Hermann; Leneweit, Gero

    2018-01-01

    Many food preparations, pharmaceuticals, and cosmetics use water-in-oil (W/O) emulsions stabilized by phospholipids. Moreover, recent technological developments try to produce liposomes or lipid coated capsules from W/O emulsions, but are faced with colloidal instabilities. To explore these

  12. Progressive deformation of ultramafic rocks accompanied with deflection of layered structure and mylonitization culminating into a pseudotachylyte-bearing seismogenic fault - a field evidence of plastic instability

    Science.gov (United States)

    Ueda, T.; Obata, M.

    2011-12-01

    recorded in limited area on a resultant fault surface. The N-S extensional arrangement of the fault system including the fault of LD structure, the depth of PST (re)crystallization and mylonitization, all indicate that the rupture nucleation occurred in extensional tectonics (Souquiere and Fabbri , 2010). The occurrence of Dol in the vicinity of the PST fault suggests that this is the very place where plastic instability accompanied with fluid chemistry evolution (from H2O-rich to CO2-rich, caused by mylonitization and hydration) of Ueda et al. (2008.) had taken place.

  13. Joint Instability and Osteoarthritis

    Directory of Open Access Journals (Sweden)

    Darryl Blalock

    2015-01-01

    Full Text Available Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA. Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA.

  14. Joint instability and osteoarthritis.

    Science.gov (United States)

    Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

    2015-01-01

    Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA.

  15. Genomic instability in mice is greater in Fanconi anemia caused by deficiency of Fancd2 than Fancg.

    Science.gov (United States)

    Reliene, Ramune; Yamamoto, Mitsuko L; Rao, P Nagesh; Schiestl, Robert H

    2010-12-01

    Fanconi anemia (FA) results from mutations in the FANC genes and is characterized by bone marrow failure, birth defects, and a high incidence of cancer. FANCG is a part of the FA core complex that is responsible for monoubiquitination of FANCD2 and FANCI. The precise role of the FA pathway is not well understood, although it may be involved in homologous recombination (HR), nonhomologous end joining, and translesion synthesis (TLS). Fancd2(-/-) mice have a more severe phenotype than Fancg(-/-), and other FA core complex-deficient mice, although both Fancg and Fancd2 belong to the same FA pathway. We hypothesized that Fancd2 deficiency results in a more severe phenotype because Fancd2 also has a FA pathway-independent function in the maintenance of genomic integrity. To test this hypothesis, we determined the level of DNA damage and genomic instability in Fancd2(-/-), Fancg(-/-), and wild-type controls. Fancd2(-/-) mice displayed a higher magnitude of chromosomal breakage and micronucleus formation than the wild-type or Fancg(-/-) mice. Also, DNA strand breaks were increased in Fancd2(-/-) but not in Fancg(-/-) mice. In addition, Fancd2(-/-) mice displayed an elevated frequency of DNA deletions, resulting from HR at the endogenous p(un) locus. In contrast, in Fancg(-/-) mice, the frequency of DNA deletions was decreased. Thus, Fancd2 but not Fancg deficiency results in elevated chromosomal/DNA breakage and permanent genome rearrangements. This provides evidence that Fancd2 plays an additional role in the maintenance of genomic stability than Fancg, which might explain the higher predisposition to cancer seen in the Fancd2(-/-) mice.

  16. Smad4 loss in mice causes spontaneous head and neck cancer with increased genomic instability and inflammation.

    Science.gov (United States)

    Bornstein, Sophia; White, Ruth; Malkoski, Stephen; Oka, Masako; Han, Gangwen; Cleaver, Timothy; Reh, Douglas; Andersen, Peter; Gross, Neil; Olson, Susan; Deng, Chuxia; Lu, Shi-Long; Wang, Xiao-Jing

    2009-11-01

    Smad4 is a central mediator of TGF-beta signaling, and its expression is downregulated or lost at the malignant stage in several cancer types. In this study, we found that Smad4 was frequently downregulated not only in human head and neck squamous cell carcinoma (HNSCC) malignant lesions, but also in grossly normal adjacent buccal mucosa. To gain insight into the importance of this observation, we generated mice in which Smad4 was deleted in head and neck epithelia (referred to herein as HN-Smad4-/- mice) and found that they developed spontaneous HNSCC. Interestingly, both normal head and neck tissue and HNSCC from HN-Smad4-/- mice exhibited increased genomic instability, which correlated with downregulated expression and function of genes encoding proteins in the Fanconi anemia/Brca (Fanc/Brca) DNA repair pathway linked to HNSCC susceptibility in humans. Consistent with this, further analysis revealed a correlation between downregulation of Smad4 protein and downregulation of the Brca1 and Rad51 proteins in human HNSCC. In addition to the above changes in tumor epithelia, both normal head and neck tissue and HNSCC from HN-Smad4-/- mice exhibited severe inflammation, which was associated with increased expression of TGF-beta1 and activated Smad3. We present what we believe to be the first single gene-knockout model for HNSCC, in which both HNSCC formation and invasion occurred as a result of Smad4 deletion. Our results reveal an intriguing connection between Smad4 and the Fanc/Brca pathway and highlight the impact of epithelial Smad4 loss on inflammation.

  17. Nonlinear ion-acoustic structures in a nonextensive electron–positron–ion–dust plasma: Modulational instability and rogue waves

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Shimin, E-mail: gsm861@126.com [School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, 710049 (China); Research Group MAC, Centrum Wiskunde and Informatica, Amsterdam, 1098XG (Netherlands); Mei, Liquan, E-mail: lqmei@mail.xjtu.edu.cn [School of Mathematics and Statistics, Xi’an Jiaotong University, Xi’an, 710049 (China); Center for Computational Geosciences, Xi’an Jiaotong University, Xi’an, 710049 (China); Sun, Anbang [Research Group MAC, Centrum Wiskunde and Informatica, Amsterdam, 1098XG (Netherlands)

    2013-05-15

    The nonlinear propagation of planar and nonplanar (cylindrical and spherical) ion-acoustic waves in an unmagnetized electron–positron–ion–dust plasma with two-electron temperature distributions is investigated in the context of the nonextensive statistics. Using the reductive perturbation method, a modified nonlinear Schrödinger equation is derived for the potential wave amplitude. The effects of plasma parameters on the modulational instability of ion-acoustic waves are discussed in detail for planar as well as for cylindrical and spherical geometries. In addition, for the planar case, we analyze how the plasma parameters influence the nonlinear structures of the first- and second-order ion-acoustic rogue waves within the modulational instability region. The present results may be helpful in providing a good fit between the theoretical analysis and real applications in future spatial observations and laboratory plasma experiments. -- Highlights: ► Modulational instability of ion-acoustic waves in a new plasma model is discussed. ► Tsallis’s statistics is considered in the model. ► The second-order ion-acoustic rogue wave is studied for the first time.

  18. Nonlinear ion-acoustic structures in a nonextensive electron–positron–ion–dust plasma: Modulational instability and rogue waves

    International Nuclear Information System (INIS)

    Guo, Shimin; Mei, Liquan; Sun, Anbang

    2013-01-01

    The nonlinear propagation of planar and nonplanar (cylindrical and spherical) ion-acoustic waves in an unmagnetized electron–positron–ion–dust plasma with two-electron temperature distributions is investigated in the context of the nonextensive statistics. Using the reductive perturbation method, a modified nonlinear Schrödinger equation is derived for the potential wave amplitude. The effects of plasma parameters on the modulational instability of ion-acoustic waves are discussed in detail for planar as well as for cylindrical and spherical geometries. In addition, for the planar case, we analyze how the plasma parameters influence the nonlinear structures of the first- and second-order ion-acoustic rogue waves within the modulational instability region. The present results may be helpful in providing a good fit between the theoretical analysis and real applications in future spatial observations and laboratory plasma experiments. -- Highlights: ► Modulational instability of ion-acoustic waves in a new plasma model is discussed. ► Tsallis’s statistics is considered in the model. ► The second-order ion-acoustic rogue wave is studied for the first time

  19. Structural instability of Y1-xPrxBa2Cu3O7-δ superconductors studied by positron annihilation lifetime

    International Nuclear Information System (INIS)

    Gou Zhenhui; Chen Feng; Zheng Shengnan; Zhao Zhongxian; Zhu Shengyun

    1995-01-01

    The temperature dependence of the positron annihilation lifetime in high-quality, single-phase Y 1-x Pr x Ba 2 Cu 3 O 7-δ has been measured from 78 to 300K for a better understanding of the origin of the normal state anomaly observed in high T c superconductivity studies. The normal state anomaly has been detected around 30 to 40K above T c for the samples with x=0.0 and 0.1, but, it was not found for the sample with x=0.2 where T c is lower than 80K. The experimental results show that the phase transition-like behavior caused by the structural instability results in the normal state anomaly which acts as a the precursor of high T c superconductivity. (orig.)

  20. Economic costs of electrical system instability and power outages caused by snakes on the Island of Guam

    Science.gov (United States)

    Fritts, T.H.

    2002-01-01

    The Brown Tree Snake, Boiga irregularis, is an introduced species on Guam where it causes frequent electrical power outages. The snake's high abundance, its propensity for climbing, and use of disturbed habitats all contribute to interruption of Guam's electrical service and the activities that depend on electrical power. Snakes have caused more than 1600 power outages in the 20-yr period of 1978–1997 and most recently nearly 200 outages per year. Single outages spanning the entire island and lasting 8 or more hours are estimated to cost in excess of $3,000,000 in lost productivity, but the costs of outages that involve only parts of the island or those of shorter durations are more difficult to quantify. Costs to the island's economy have exceeded $4.5 M $4.5M"> per year over a 7-yr period without considering repair costs, damage to electrical equipment, and lost revenues. Snakes pose the greatest problem on high voltage transmission lines, on transformers, and inside electrical substations.

  1. Vertical structure of the vhf backscattering region in the equatorial electrojet and the gradient drift instability

    International Nuclear Information System (INIS)

    Fejer, B.G.; Farley, D.T.; Balsley, B.B.; Woodman, R.F.

    1974-01-01

    Radar measurements made with high spatial resolution and large dynamic range at the Jicamarca Radar Observatory near the time of reversal of the electrojet current provide further proof that the gradient drift instability is in fact responsible for the type-2 irregularities. Echoes are received over a much wider range of altitudes at night than during the day, partly because of the change in character of the background electron density profile and partly because of recombination effects, which can be important during the day. One must be cautious, particularly at night, in associating the mean Doppler shift of oblique radar echoes with the maximum east--west electron drift velocity

  2. Functional Instability of the Ankle Joint: Etiopathogenesis

    Directory of Open Access Journals (Sweden)

    Aydan ÖRSÇELİK

    2016-09-01

    Full Text Available Ankle sprain is one of the most common sports injuries. Chronic ankle instability is a common complication of ankle sprains. Two causes of chronic ankle instability are mechanical instability and functional instability. It is important to understand functional instability etiopathogenesis of the ankle joint in order to guide diagnosis and treatment. This article aims to understand the etiopathogenesis of functional ankle instability.

  3. BUCLASP 2: A computer program for instability analysis of biaxially loaded composite stiffened panels and other structures

    Science.gov (United States)

    Tripp, L. L.; Tamekuni, M.; Viswanathan, A. V.

    1973-01-01

    The use of the computer program BUCLASP2 is described. The program is intended for linear instability analyses of structures such as unidirectionally stiffened panels. Any structure that has a constant cross section in one direction, that may be idealized as an assemblage of beam elements and laminated flat and curved plant strip elements can be analyzed. The loadings considered are combinations of axial compressive loads and in-plane transverse loads. The two parallel ends of the panel must be simply supported and arbitrary elastic boundary conditions may be imposed along any one or both external longitudinal side. This manual consists of instructions for use of the program with sample problems, including input and output information. The theoretical basis of BUCLASP2 and correlations of calculated results with known solutions, are presented.

  4. Vertical structure of the VHF backscattering region in the equatorial electrojet and the gradient drift instability

    International Nuclear Information System (INIS)

    Fejer, B.G.; Farley, D.T.; Balsley, B.B.; Woodman, R.F.

    1975-01-01

    Radar measurements made with high spatial resolution and large dynamic range at the Jicamarca Radar Observatory near the time of reversal of the electrojet current provide further proof that the gradient drift instability is in fact responsible for the type 2 irregularities. Echoes are received over a much wider range of altitudes at night than during the day partly because of the change in character of the background electron density profile and partly because of recombination effects, which can be important during the day. It is also shown that one must be cautious, particularly at night, in associating the mean Doppler shift of oblique radar echoes with the maximum east-west electron drift velocity

  5. Effects of Replication and Transcription on DNA Structure-Related Genetic Instability.

    Science.gov (United States)

    Wang, Guliang; Vasquez, Karen M

    2017-01-05

    Many repetitive sequences in the human genome can adopt conformations that differ from the canonical B-DNA double helix (i.e., non-B DNA), and can impact important biological processes such as DNA replication, transcription, recombination, telomere maintenance, viral integration, transposome activation, DNA damage and repair. Thus, non-B DNA-forming sequences have been implicated in genetic instability and disease development. In this article, we discuss the interactions of non-B DNA with the replication and/or transcription machinery, particularly in disease states (e.g., tumors) that can lead to an abnormal cellular environment, and how such interactions may alter DNA replication and transcription, leading to potential conflicts at non-B DNA regions, and eventually result in genetic stability and human disease.

  6. A photoionization instability in the early intergalactic medium

    Science.gov (United States)

    Hogan, Craig J.

    1992-01-01

    It is argued that any fairly uniform source of ionizing photons can be the cause of an instability in the pregalactic medium on scales larger than a photon path length. Underdense regions receive more ionizing energy per atom and reach higher temperature and entropy, driving the density down still further. Fluctuations created by this instability can lead to the formation of structures resembling protogalaxies and intergalactic clouds, obviating the need for gas clouds or density perturbations of earlier cosmological provenance, as is usually assumed in theories of galaxy and structure formation. Characteristic masses for clouds produced by the instability, with log mass in solar units plotted against log radius in kpc, are illustrated.

  7. Generation of mesoscale F layer structure and electric fields by the combined Perkins and Es layer instabilities, in simulations

    Directory of Open Access Journals (Sweden)

    R. B. Cosgrove

    2007-07-01

    Full Text Available The generic equilibrium configuration of the nighttime midlatitude ionosphere consists of an F layer held up against gravity by winds and/or electric fields, and a sporadic E (Es layer located by a sheared wind field, which experiences the same electric fields as the F layer. This configuration is subject to two large-scale (e.g. >10 km "layer instabilities": one of the F layer known as the Perkins instability, and another of the Es layer which has been called the Es layer instability. Electric fields on scales larger than (about 10 km map very efficiently between the Es and F layers, and the two instabilities have a similar geometry, allowing them to interact with one another. As shown through a linear growth rate analysis, the two most important parameters governing the interaction are the relative horizontal velocity between the Es and F layers, and the integrated conductivity ratio ΣH/ΣPF, where ΣH and ΣPF are the field line integrated Hall conductivity of the Es layer, and the field line integrated Pedersen conductivity of the F layer, respectively. For both large and small relative velocities the growth rate was found to be more than double that of the Perkins instability alone, when ΣHΣPF=1.8. However, the characteristic eigenmode varies considerably with relative velocity, and different nonlinear behavior is expected in these two cases. As a follow up to the linear growth rate analysis, we explore in this article the nonlinear evolution of the unstable coupled system subject to a 200 km wavelength initial perturbation of the F layer, using a two-dimensional numerical solution of the two-fluid equations, as a function of relative horizontal velocity and ΣHΣPF. We find that when ΣHΣPF⪝0.5 the Perkins instability is able to control the dynamics and modulate the F layer altitude in 2 to 3 h time. However, the electric fields remain small until the altitude modulation is extremely large, and even then they are not large enough to

  8. [Sleep structure instability in healthy men under conditions of 105-day isolation experiment "Mars-105"].

    Science.gov (United States)

    Kovrov, G V; Posokhov, S I; Posokhov, S S; Zavalko, I M; Ponomareva, I P

    2013-01-01

    Night-to-night stability of falling asleep and duration of wakefulness in the sleep was studied in six healthy male subjects under conditions of 105-day isolation experiment "Mars-105". Polysomnography records were carried out in each subject during five nights taken in regular intervals within the experiment. Three subjects demonstrated high stability of falling asleep and wakefulness in sleep (group I), whereas in the remaining three subjects stability of these characteristics was low (group [I). Delta-sleep was shown to be deepened in subjects of group II (significant prevalence of stage 4 (47.3 min) over stage 3 (32.9 min)). In subjects of group I, the duration of stage 3 was 44.9 min and that of stage 4 was 26.6 min. We suggest that night-to-night instability of falling asleep and duration of wakefulness in sleep in combination with delta sleep is the special individual form of sleep adaptation to conditions of chronic isolation stress.

  9. Suppression of photo-bias induced instability for amorphous indium tungsten oxide thin film transistors with bi-layer structure

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Po-Tsun, E-mail: ptliu@mail.nctu.edu.tw; Chang, Chih-Hsiang; Chang, Chih-Jui [Department of Photonics and Institute of Electro-Optical Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

    2016-06-27

    This study investigates the instability induced by bias temperature illumination stress (NBTIS) for an amorphous indium-tungsten-oxide thin film transistor (a-IWO TFT) with SiO{sub 2} backchannel passivation layer (BPL). It is found that this electrical degradation phenomenon can be attributed to the generation of defect states during the BPL process, which deteriorates the photo-bias stability of a-IWO TFTs. A method proposed by adding an oxygen-rich a-IWO thin film upon the a-IWO active channel layer could effectively suppress the plasma damage to channel layer during BPL deposition process. The bi-layer a-IWO TFT structure with an oxygen-rich back channel exhibits superior electrical reliability of device under NBTIS.

  10. Streaming gravity mode instability

    International Nuclear Information System (INIS)

    Wang Shui.

    1989-05-01

    In this paper, we study the stability of a current sheet with a sheared flow in a gravitational field which is perpendicular to the magnetic field and plasma flow. This mixing mode caused by a combined role of the sheared flow and gravity is named the streaming gravity mode instability. The conditions of this mode instability are discussed for an ideal four-layer model in the incompressible limit. (author). 5 refs

  11. Interplay of structural instability and lattice dynamics in Ni{sub 2}MnAl shape memory alloys

    Energy Technology Data Exchange (ETDEWEB)

    Mehaddene, T.

    2007-02-12

    The work presented here is devoted to investigate the interplay of lattice dynamics and structural instability in Ni{sub 2}MnAl shape memory alloys. Inelastic neutron scattering is used to get more insight on the dynamic precursors of structural instability in Ni{sub 2}MnAl. Differential Scanning Calorimetry was used to characterise the martensitic transition in Ni{sub 2}MnAl alloys. Effects of composition and heat treatments have been investigated. The measured martensitic transition temperature in Ni-Mn-Al alloys depends linearly on the valence electron concentration. Two single crystals with different compositions have been succesfully grown using the Czochralski technique. Acoustic and optical phonon modes have been measured at room temperature in the high symmetry directions of the cubic B2 phase. The force constants have been fitted to the measured data using the Born-von Karman model. The character of the phonon softening measured in Ni{sub 2}MnAl corresponds to the pattern of atomic displacements of the modulations 2M, 10M, 12M and 14M observed in bulk and thin-films of Ni{sub 2}MnAl. The effect of the composition on the lattice instability has been investigated by measuring normal modes of vibration in two different crystals, Ni{sub 51}Mn{sub 18}Al{sub 31} and Ni{sub 53}Mn{sub 22}Al{sub 25}, with e/a ratios of 7.29 and 7.59 respectively. The stabilisation of a single L2{sub 1} phase in Ni{sub 2}MnAl by annealing a Ni{sub 51}Mn{sub 18}Al{sub 31} single crystal at 673 K during 45 days has been attempted. Despite of the long-time annealing, a single L2{sub 1} phase could not be stabilised because of either a slow diffusion kinetics or the establishment of an equilibrium between the L2{sub 1} and the B2 phases. Phonon measurements of the TA{sub 2}[{xi}{xi}0] branch in the annealed sample revealed a substantial effect. The wiggle, associated with the anomalous softening, is still present but the degree of softening is smaller below 673 K and changes

  12. Using instability to reconfigure smart structures in a spring-mass model

    Science.gov (United States)

    Zhang, Jiaying; McInnes, Colin R.

    2017-07-01

    Multistable phenomenon have long been used in mechanism design. In this paper a subset of unstable configurations of a smart structure model will be used to develop energy-efficient schemes to reconfigure the structure. This new concept for reconfiguration uses heteroclinic connections to transition the structure between different unstable equal-energy states. In an ideal structure model zero net energy input is required for the reconfiguration, compared to transitions between stable equilibria across a potential barrier. A simple smart structure model is firstly used to identify sets of equal-energy unstable configurations using dynamical systems theory. Dissipation is then added to be more representative of a practical structure. A range of strategies are then used to reconfigure the smart structure using heteroclinic connections with different approaches to handle dissipation.

  13. Expression of the MAP kinase phosphatase DUSP4 is associated with microsatellite instability in colorectal cancer (CRC) and causes increased cell proliferation.

    Science.gov (United States)

    Gröschl, Benedikt; Bettstetter, Marcus; Giedl, Christian; Woenckhaus, Matthias; Edmonston, Tina; Hofstädter, Ferdinand; Dietmaier, Wolfgang

    2013-04-01

    DUSP4 (MKP-2), a member of the mitogen-activated protein kinase phosphatase (MKP) family and potential tumor suppressor, negatively regulates the MAPKs (mitogen-activated protein kinases) ERK, p38 and JNK. MAPKs play a crucial role in cancer development and progression. Previously, using microarray analyses we found a conspicuously frequent overexpression of DUSP4 in colorectal cancer (CRC) with high frequent microsatellite instability (MSI-H) compared to microsatellite stable (MSS) CRC. Here we studied DUSP4 expression on mRNA level in 38 CRC (19 MSI-H and 19 MSS) compared to matched normal tissue as well as in CRC cell lines by RT-qPCR. DUSP4 was overexpressed in all 19 MSI-H tumors and in 14 MSS tumors. Median expression levels in MSI-H tumors were significantly higher than in MSS-tumors (p CRC cell lines showed 6.8-fold higher DUSP4 mRNA levels than MSS cell lines. DUSP4 expression was not regulated by promoter methylation since no methylation was found by quantitative methylation analysis of DUSP4 promoter in CRC cell lines neither in tumor samples. Furthermore, no DUSP4 mutation was found on genomic DNA level in four CRC cell lines. DUSP4 overexpression in CRC cell lines through DUSP4 transfection caused upregulated expression of MAPK targets CDC25A, CCND1, EGR1, FOS, MYC and CDKN1A in HCT116 as well as downregulation of mismatch repair gene MSH2 in SW480. Furthermore, DUSP4 overexpression led to increased proliferation in CRC cell lines. Our findings suggest that DUSP4 acts as an important regulator of cell growth within the MAPK pathway and causes enhanced cell growth in MSI-H CRC. Copyright © 2012 UICC.

  14. AN ORIGIN OF MULTIPLE RING STRUCTURE AND HIDDEN PLANETS IN HL TAU: A UNIFIED PICTURE BY SECULAR GRAVITATIONAL INSTABILITY

    International Nuclear Information System (INIS)

    Takahashi, Sanemichi Z.; Inutsuka, Shu-ichiro

    2016-01-01

    Recent ALMA observation has revealed multiple ring structures formed in a protoplanetary disk around HL Tau. Prior to the ALMA observation of HL Tau, theoretical analysis of secular gravitational instability (GI) described a possible formation of multiple ring structures with separations of 13 au around a radius of 100 au in protoplanetary disks under certain conditions. In this article, we reanalyze the viability of secular GI by adopting the physical values inferred from the observations. We derive the radial distributions of the most unstable wavelength and the growth timescale of secular GI and verify that secular GI can form the ring structures observed in HL Tau. When a turbulent viscosity coefficient α remains small in the inner region of the disk, secular GI grows in the whole disk. Thus, the formation of planetary mass objects should occur first in the inner region as a result of gravitational fragmentation after the nonlinear growth of secular GI. In this case, the resulting objects are expected to create gaps at r  ∼ 10 au and ∼30 au. As a result, all ring structures in HL Tau can be created by secular GI. If this scenario is realized in HL Tau, the outer region corresponds to the earlier growth phase of the most unstable mode of secular GI, and the inner region corresponds to the outcome of the nonlinear growth of secular GI. Therefore, this interpretation suggests that we are possibly witnessing both the beginning and the end of planet formation in HL Tau.

  15. AN ORIGIN OF MULTIPLE RING STRUCTURE AND HIDDEN PLANETS IN HL TAU: A UNIFIED PICTURE BY SECULAR GRAVITATIONAL INSTABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Sanemichi Z. [Astronomical Institute, Tohoku University, 6-3 Aoba, Aramaki-aza, Aoba-ku, Sendai, Miyagi (Japan); Inutsuka, Shu-ichiro, E-mail: sanemichi@astr.tohoku.ac.jp, E-mail: inutsuka@nagoya-u.jp [Department of Physics, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8602 (Japan)

    2016-12-01

    Recent ALMA observation has revealed multiple ring structures formed in a protoplanetary disk around HL Tau. Prior to the ALMA observation of HL Tau, theoretical analysis of secular gravitational instability (GI) described a possible formation of multiple ring structures with separations of 13 au around a radius of 100 au in protoplanetary disks under certain conditions. In this article, we reanalyze the viability of secular GI by adopting the physical values inferred from the observations. We derive the radial distributions of the most unstable wavelength and the growth timescale of secular GI and verify that secular GI can form the ring structures observed in HL Tau. When a turbulent viscosity coefficient α remains small in the inner region of the disk, secular GI grows in the whole disk. Thus, the formation of planetary mass objects should occur first in the inner region as a result of gravitational fragmentation after the nonlinear growth of secular GI. In this case, the resulting objects are expected to create gaps at r  ∼ 10 au and ∼30 au. As a result, all ring structures in HL Tau can be created by secular GI. If this scenario is realized in HL Tau, the outer region corresponds to the earlier growth phase of the most unstable mode of secular GI, and the inner region corresponds to the outcome of the nonlinear growth of secular GI. Therefore, this interpretation suggests that we are possibly witnessing both the beginning and the end of planet formation in HL Tau.

  16. Tearing instabilities in turbulence

    International Nuclear Information System (INIS)

    Ishizawa, A.; Nakajima, N.

    2009-01-01

    Full text: Effects of micro-turbulence on tearing instabilities are investigated by numerically solving a reduced set of two-fluid equations. Micro-turbulence excites both large-scale and small-scale Fourier modes through energy transfer due to nonlinear mode coupling. The energy transfer to large scale mode does not directly excite tearing instability but it gives an initiation of tearing instability. When tearing instability starts to grow, the excited small scale mode plays an important role. The mixing of magnetic flux by micro-turbulence is the dominant factor of non-ideal MHD effect at the resonant surface and it gives rise to magnetic reconnection which causes tearing instability. Tearing instabilities were investigated against static equilibrium or flowing equilibrium so far. On the other hand, the recent progress of computer power allows us to investigate interactions between turbulence and coherent modes such as tearing instabilities in magnetically confined plasmas by means of direct numerical simulations. In order to investigate effects of turbulence on tearing instabilities we consider a situation that tearing mode is destabilized in a quasi-equilibrium including micro-turbulence. We choose an initial equilibrium that is unstable against kinetic ballooning modes and tearing instabilities. Tearing instabilities are current driven modes and thus they are unstable for large scale Fourier modes. On the other hand kinetic ballooning modes are unstable for poloidal Fourier modes that are characterized by ion Larmor radius. The energy of kinetic ballooning modes spreads over wave number space through nonlinear Fourier mode coupling. We present that micro-turbulence affects tearing instabilities in two different ways by three-dimensional numerical simulation of a reduced set of two-fluid equations. One is caused by energy transfer to large scale modes, the other is caused by energy transfer to small scale modes. The former is the excitation of initial

  17. Solution strategies for linear and nonlinear instability phenomena for arbitrarily thin shell structures

    International Nuclear Information System (INIS)

    Eckstein, U.; Harte, R.; Kraetzig, W.B.; Wittek, U.

    1983-01-01

    In order to describe nonlinear response and instability behaviour the paper starts with the total potential energy considering the basic kinematic equations of a consistent nonlinear shell theory for large displacements and moderate rotations. The material behaviour is assumed to be hyperelastic and isotropic. The incrementation and discretization of the total potential energy leads to the tangent stiffness relation, which is the central equation of computational algorithms based on combined incremental and iterative techniques. Here a symmetrized form of the RIKS/WEMPNER-algorithm for positive and negative load incrementation represents the basis of the nonlinear solution technique. To detect secondary equilibrium branches at points of neutral equilibrium within nonlinear primary paths a quadratic eigenvalue-problem has to be solved. In order to follow those complicated nonlinear response phenomena the RIKS/WEMPNER incrementation/iteration process is combined with a simultaneous solution of the linearized quadratic eigenvalue-problem. Additionally the essentials of a recently derived family of arbitrarily curved shell elements for linear (LACS) and geometrically nonlinear (NACS) shell problems are presented. The main advantage of these elements is the exact description of all geometric properties as well as the energy-equivalent representation of the applied loads in combination with an efficient algorithm to form the stiffness submatrices. Especially the NACS-elements are designed to improve the accuracy of the solution in the deep postbuckling range including moderate rotations. The derived finite elements and solution strategies are applied to a certain number of typical shell problems to prove the precision of the shell elements and to demonstrate the possibilities of tracing linear and nonlinear bifurcation problems as well as snap-through phenomena with and without secondary bifurcation branches. (orig.)

  18. Lattice instabilities and structural phase transformations in La2CuO4 superconductors and insulators

    International Nuclear Information System (INIS)

    Axe, J.D.

    1991-01-01

    Soft-mode structural phase transformations, common in many perovskite-based materials, are also found in La 2 CuO 4 and structurally related oxides. The resulting phase behavior is rather complex, but is a natural consequence of the degeneracy of the soft phonon order parameters. This paper reviews the structural and lattice-dynamical results and their interpretation based upon mean-field statistical mechanical models

  19. Simulation of Structures Exhibiting Instability Under Thermal-Mechanical Transient Loading

    Science.gov (United States)

    2015-08-25

    stiffness of the system becomes singular when the structure loses stability. The tangent stiffness matrix of the system can be obtained from Eqs. (7) and...L. Virgin , Vibration of axially loaded structures, Cambridge University Press, 2007. [4] A. Przekoo and S. A. Rizzi, Dynamic snap-through of thin...walled structures by a reduced-order model, AIAA Journal, 45 (10) (2007) 2510-2519. [5] Y. Chandra, I. Stanciulescu, L. N. Virgin , T. G. Eason, and S. M

  20. Spondylolisthesis and Posterior Instability

    International Nuclear Information System (INIS)

    Niggemann, P.; Beyer, H.K.; Frey, H.; Grosskurth, D.; Simons, P.; Kuchta, J.

    2009-01-01

    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

  1. 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.

  2. Instability and associated roll structure of Marangoni convection in high Prandtl number liquid bridge with large aspect ratio

    Science.gov (United States)

    Yano, T.; Nishino, K.; Kawamura, H.; Ueno, I.; Matsumoto, S.

    2015-02-01

    This paper reports the experimental results on the instability and associated roll structures (RSs) of Marangoni convection in liquid bridges formed under the microgravity environment on the International Space Station. The geometry of interest is high aspect ratio (AR = height/diameter ≥ 1.0) liquid bridges of high Prandtl number fluids (Pr = 67 and 207) suspended between coaxial disks heated differentially. The unsteady flow field and associated RSs were revealed with the three-dimensional particle tracking velocimetry. It is found that the flow field after the onset of instability exhibits oscillations with azimuthal mode number m = 1 and associated RSs traveling in the axial direction. The RSs travel in the same direction as the surface flow (co-flow direction) for 1.00 ≤ AR ≤ 1.25 while they travel in the opposite direction (counter-flow direction) for AR ≥ 1.50, thus showing the change of traveling directions with AR. This traveling direction for AR ≥ 1.50 is reversed to the co-flow direction when the temperature difference between the disks is increased to the condition far beyond the critical one. This change of traveling directions is accompanied by the increase of the oscillation frequency. The characteristics of the RSs for AR ≥ 1.50, such as the azimuthal mode of oscillation, the dimensionless oscillation frequency, and the traveling direction, are in reasonable agreement with those of the previous sounding rocket experiment for AR = 2.50 and those of the linear stability analysis of an infinite liquid bridge.

  3. Direct observation of electrothermal instability structures on intensely Ohmically heated aluminum with current flowing in a surface skin layer

    Science.gov (United States)

    Awe, Thomas

    2017-10-01

    Implosions on the Z Facility assemble high-energy-density plasmas for radiation effects and ICF experiments, but achievable stagnation pressures and temperatures are degraded by the Magneto-Rayleigh-Taylor (MRT) instability. While the beryllium liners (tubes) used in Magnetized Liner Inertial Fusion (MagLIF) experiments are astonishingly smooth (10 to 50 nm RMS roughness), they also contain distributed micron-scale resistive inclusions, and large MRT amplitudes are observed. Early in the implosion, an electrothermal instability (ETI) may provide a perturbation which greatly exceeds the initial surface roughness of the liner. Resistive inhomogeneities drive nonuniform current density and Joule heating, resulting in locally higher temperature, and thus still higher resistivity. Such unstable temperature and pressure growth produce density perturbations which seed MRT. For MagLIF liners, ETI seeding of MRT has been inferred by evaluating late-time MRT, but a direct observation of ETI is not made. ETI is directly observed on the surface of 1.0-mm-diameter solid Al rods pulsed to 1 MA in 100 ns via high resolution gated optical imaging (2 ns temporal and 3 micron spatial resolution). Aluminum 6061 alloy rods, with micron-scale resistive inclusions, consistently first demonstrate overheating from distinct, 10-micron-scale, sub-eV spots, which 5-10 ns later merge into azimuthally stretched elliptical spots and discrete strata (40-100 microns wide by 10 microns tall). Axial plasma filaments form shortly thereafter. Surface plasma can be suppressed for rods coated with dielectric, enabling extended study of the evolution of stratified ETI structures, and experimental inference of ETI growth rates. This fundamentally new and highly 3-dimensional dataset informs ETI physics, including when the ETI seed of MRT may be initiated.

  4. Interfacial wave theory for dendritic structure of a growing needle crystal. I - Local instability mechanism. II - Wave-emission mechanism at the turning point

    Science.gov (United States)

    Xu, Jian-Jun

    1989-01-01

    The complicated dendritic structure of a growing needle crystal is studied on the basis of global interfacial wave theory. The local dispersion relation for normal modes is derived in a paraboloidal coordinate system using the multiple-variable-expansion method. It is shown that the global solution in a dendrite growth process incorporates the morphological instability factor and the traveling wave factor.

  5. Ducks in space: from nonlinear absolute instability to noise-sustained structures in a pattern-forming system

    Science.gov (United States)

    Avitabile, D.; Desroches, M.; Knobloch, E.; Krupa, M.

    2017-11-01

    A subcritical pattern-forming system with nonlinear advection in a bounded domain is recast as a slow-fast system in space and studied using a combination of geometric singular perturbation theory and numerical continuation. Two types of solutions describing the possible location of stationary fronts are identified, whose origin is traced to the onset of convective and absolute instability when the system is unbounded. The former are present only for non-zero upstream boundary conditions and provide a quantitative understanding of noise-sustained structures in systems of this type. The latter correspond to the onset of a global mode and are present even with zero upstream boundary conditions. The role of canard trajectories in the nonlinear transition between these states is clarified and the stability properties of the resulting spatial structures are determined. Front location in the convective regime is highly sensitive to the upstream boundary condition, and its dependence on this boundary condition is studied using a combination of numerical continuation and Monte Carlo simulations of the partial differential equation. Statistical properties of the system subjected to random or stochastic boundary conditions at the inlet are interpreted using the deterministic slow-fast spatial dynamical system.

  6. Structural instability of atmospheric flows under perturbations of the mass balance and effect in transport calculations

    International Nuclear Information System (INIS)

    Núñez, M A; Mendoza, R

    2015-01-01

    Several methods to estimate the velocity field of atmospheric flows, have been proposed to the date for applications such as emergency response systems, transport calculations and for budget studies of all kinds. These applications require a wind field that satisfies the conservation of mass but, in general, estimated wind fields do not satisfy exactly the continuity equation. An approach to reduce the effect of using a divergent wind field as input in the transport-diffusion equations, was proposed in the literature. In this work, a linear local analysis of a wind field, is used to show analytically that the perturbation of a large-scale nondivergent flow can yield a divergent flow with a substantially different structure. The effects of these structural changes in transport calculations are illustrated by means of analytic solutions of the transport equation

  7. Genome instability in the context of chromatin structure and fragile sites

    Czech Academy of Sciences Publication Activity Database

    Bártová, Eva; Galiová-Šustáčková, Gabriela; Legartová, Soňa; Stixová, Lenka; Jugová, Alžbeta; Kozubek, Stanislav

    2010-01-01

    Roč. 20, č. 3 (2010), s. 181-194 ISSN 1045-4403 R&D Projects: GA MŠk ME 919; GA ČR(CZ) GAP302/10/1022 Grant - others:GA MŠk(CZ) LC06027; GA MŠk(CZ) LC535 Program:LC; LC Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702 Keywords : gene amplification * fragile sites * chromatin structure Subject RIV: BO - Biophysics Impact factor: 4.111, year: 2010

  8. Evolution of dispersion fuel meat structure caused by interface reaction

    International Nuclear Information System (INIS)

    Xing Zhonghu; Ying Shihao

    2000-01-01

    In reactor operation, the resultant layers are formed by interdiffusion at the fuel particle-matrix interfaces of U 3 Si 2 -Al dispersion fuel. This results in the evolution of meat structure. On the basis of Monte-Carlo method, the author developed simulation method of fuel meat, and simulated the stochastic space locations of spherical fuel particles in the meat. The fuel volume fraction is 43%, and the particles are in definite size distribution. For the 13551 simulated particle samples, the evolution of meat structure is calculated with layer thickness ranging from 0 to 16 μm. The parameters of meat structure include the U 3 Si 2 fuel volume fraction, resultant layer volume fraction, Al matrix volume fraction, particle contact probability and overlap degree as functions of layer thickness

  9. INTERNAL STRUCTURE OF ASTEROIDS HAVING SURFACE SHEDDING DUE TO ROTATIONAL INSTABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Hirabayashi, Masatoshi [Research Associate, Colorado Center for Astrodynamics Research, Aerospace Engineering Sciences, University of Colorado Boulder (United States); Sánchez, Diego Paul [Senior Research Associate, Colorado Center for Astrodynamics Research, Aerospace Engineering Sciences, University of Colorado Boulder (United States); Scheeres, Daniel J., E-mail: masatoshi.hirabayashi@colorado.edu [Richard Seebass Chair, Professor, Colorado Center for Astrodynamics Research, Aerospace Engineering Sciences, University of Colorado Boulder (United States)

    2015-07-20

    Surface shedding of an asteroid is a failure mode where surface materials fly off due to strong centrifugal forces beyond the critical spin period, while the internal structure does not deform significantly. This paper proposes a possible structure of an asteroid interior that leads to surface shedding due to rapid rotation rates. A rubble pile asteroid is modeled as a spheroid composed of a surface shell and a concentric internal core, the entire assembly called the test body. The test body is assumed to be uniformly rotating around a constant rotation axis. We also assume that while the bulk density and the friction angle are constant, the cohesion of the surface shell is different from that of the internal core. First, developing an analytical model based on limit analysis, we provide the upper and lower bounds for the actual surface shedding condition. Second, we use a Soft-sphere Discrete Element Method (SSDEM) to study dynamical deformation of the test body due to a quasi-static spin-up. In this paper we show the consistency of both approaches. Additionally, the SSDEM simulations show that the initial failure always occurs locally and not globally. In addition, as the core becomes larger, the size of lofted components becomes smaller. These results imply that if there is a strong core in a progenitor body, surface shedding is the most likely failure mode.

  10. INTERNAL STRUCTURE OF ASTEROIDS HAVING SURFACE SHEDDING DUE TO ROTATIONAL INSTABILITY

    International Nuclear Information System (INIS)

    Hirabayashi, Masatoshi; Sánchez, Diego Paul; Scheeres, Daniel J.

    2015-01-01

    Surface shedding of an asteroid is a failure mode where surface materials fly off due to strong centrifugal forces beyond the critical spin period, while the internal structure does not deform significantly. This paper proposes a possible structure of an asteroid interior that leads to surface shedding due to rapid rotation rates. A rubble pile asteroid is modeled as a spheroid composed of a surface shell and a concentric internal core, the entire assembly called the test body. The test body is assumed to be uniformly rotating around a constant rotation axis. We also assume that while the bulk density and the friction angle are constant, the cohesion of the surface shell is different from that of the internal core. First, developing an analytical model based on limit analysis, we provide the upper and lower bounds for the actual surface shedding condition. Second, we use a Soft-sphere Discrete Element Method (SSDEM) to study dynamical deformation of the test body due to a quasi-static spin-up. In this paper we show the consistency of both approaches. Additionally, the SSDEM simulations show that the initial failure always occurs locally and not globally. In addition, as the core becomes larger, the size of lofted components becomes smaller. These results imply that if there is a strong core in a progenitor body, surface shedding is the most likely failure mode

  11. Recurrent RECQL4 Imbalance and Increased Gene Expression Levels Are Associated with Structural Chromosomal Instability in Sporadic Osteosarcoma

    Directory of Open Access Journals (Sweden)

    Georges Maire

    2009-03-01

    Full Text Available Osteosarcoma (OS is an aggressive bone tumor with complex abnormal karyotypes and a highly unstable genome, exhibiting both numerical- and structural-chromosomal instability (N- and S-CIN. Chromosomal rearrangements and genomic imbalances affecting 8q24 are frequent in OS. RECQL4 gene maps to this cytoband and encodes a putative helicase involved in the fidelity of DNA replication and repair. This protective genomic function of the protein is relevant because often patients with Rothmund-Thomson syndrome have constitutional mutations of RECQL4 and carry a very high risk of developing OS. To determine the relative level of expression of RECQL4 in OS, 18 sporadic tumors were studied by reverse transcription–polymerase chain reaction. All tumors overexpressed RECQL4 in comparison to control osteoblasts, and fluorescence in situ hybridization analysis of tumor DNA showed that expression levels were strongly copy number–dependent. Relative N- and S-CIN levels were determined by classifying copy number transitions within array comparative genomic hybridization profiles and by enumerating the frequency of break-apart fluorescence in situ hybridization within 8q24 using region-specific and control probes. Although there was no evidence that disruption of 8q24 in OS led to an elevated expression of RECQL4, there was a marked association between increased overall levels of S-CIN, determined by copy number transition frequency and higher levels of RECQL4.

  12. Investigation of Parametric Instability of the Planetary Gear under Speed Fluctuations

    Directory of Open Access Journals (Sweden)

    Xinghui Qiu

    2017-01-01

    Full Text Available Planetary gear is widely used in engineering and usually has symmetrical structure. As the number of teeth in contact changes during rotation, the time-varying mesh stiffness parametrically excites the planetary gear and may cause severe vibrations and instabilities. Taking speed fluctuations into account, the time-varying mesh stiffness is frequency modulated, and therefore sideband instabilities may arise and original instabilities are significantly affected. Considering two different speed fluctuations, original and sideband instabilities are numerically and analytically investigated. A rotational lumped-parameter model of the planetary gear is developed, in which the time-varying mesh stiffness, input speed fluctuations, and damping are considered. Closed-form approximations of instability boundaries for primary and combination instabilities are obtained by perturbation analysis and verified by numerical analysis. The effects of speed fluctuations and damping on parametric instability are systematically examined. Because of the frequency modulation, whether a parametric instability occurs cannot be simply predicted by the planet meshing phase which is applicable to constant speed. Besides adjusting the planet meshing phase, speed fluctuation supplies a new thought to minimize certain instability by adjusting the amplitude or frequency of the speed fluctuation. Both original and sideband instabilities are shrunken by damping, and speed fluctuation further shrinks the original instability.

  13. Effects of Ionizing Radiation on Cellular Structures, Induced Instability, and Carcinogenesis

    International Nuclear Information System (INIS)

    Resat, Marianne S.; Arthurs, Benjamin J.; Estes, Brian J.; Morgan, william F.

    2006-01-01

    According to the American Cancer Society, the United States can expect 1,368,030 new cases of cancer in 2004 [1]. Among the many carcinogens Americans are exposed to, ionizing radiation will contribute to this statistic. Humans live in a radiation environment. Ionizing radiation is in the air we breathe, the earth we live on, and the food we eat. Man-made radiation adds to this naturally occurring radiation level thereby increasing the chance for human exposure. For many decades the scientific community, governmental regulatory bodies, and concerned citizens have struggled to estimate health risks associated with radiation exposures, particularly at low doses. While cancer induction is the primary concern and the most important somatic effect of exposure to ionizing radiation, potential health risks do not involve neoplastic diseases exclusively but also include somatic mutations that might contribute to birth defects and ocular maladies, and heritable mutations that might impact on disease risks in future generations. Consequently it is important we understand the effect of ionizing radiation on cellular structures and the subsequent long-term health risks associated with exposure to ionizing radiation

  14. Subdiffusive master equation with space-dependent anomalous exponent and structural instability

    Science.gov (United States)

    Fedotov, Sergei; Falconer, Steven

    2012-03-01

    We derive the fractional master equation with space-dependent anomalous exponent. We analyze the asymptotic behavior of the corresponding lattice model both analytically and by Monte Carlo simulation. We show that the subdiffusive fractional equations with constant anomalous exponent μ in a bounded domain [0,L] are not structurally stable with respect to the nonhomogeneous variations of parameter μ. In particular, the Gibbs-Boltzmann distribution is no longer the stationary solution of the fractional Fokker-Planck equation whatever the space variation of the exponent might be. We analyze the random distribution of μ in space and find that in the long-time limit, the probability distribution is highly intermediate in space and the behavior is completely dominated by very unlikely events. We show that subdiffusive fractional equations with the nonuniform random distribution of anomalous exponent is an illustration of a “Black Swan,” the low probability event of the small value of the anomalous exponent that completely dominates the long-time behavior of subdiffusive systems.

  15. Structural instabilities of high temperature alloys and their use in advanced high temperature gas cooled reactors

    International Nuclear Information System (INIS)

    Schuster, H.; Ennis, P.J.; Nickel, H.; Czyrska-Filemonowicz, A.

    1989-01-01

    High-temperature, iron-nickel and nickel based alloys are the candidate heat exchanger materials for advanced high temperature gas-cooled reactors supplying process heat for coal gasification, where operation temperatures can reach 850-950 deg. C and service lives of more than 100,000 h are necessary. In the present paper, typical examples of structural changes which occur in two representative alloys (Alloy 800 H, Fe-32Ni-20Cr and Alloy 617, Ni-22Cr-12Co-9Mo-1Al) during high temperature exposure will be given and the effects on the creep rupture properties discussed. At service temperatures, precipitation of carbides occurs which has a significant effect on the creep behaviour, especially in the early stages of creep when the precipitate particles are very fine. During coarsening of the carbides, carbides at grain boundaries restrict grain boundary sliding which retards the development of creep damage. In the service environments, enhanced carbide precipitation may occur due to the ingress of carbon from the environment (carburization). Although the creep rate is not adversely affected, the ductility of the carburized material at low and intermediate temperatures is very low. During simulated service exposures, the formation of surface corrosion scales, the precipitation of carbides and the formation of internal oxides below the surface leads to depletion of the matrix in the alloying elements involved in the corrosion processes. In thin-walled tubes the depletion of Cr due to Cr 2 O 3 formation on the surface can lead to a loss of creep strength. An additional depletion effect resulting from environmental-metal reactions is the loss of carbon (decarburization) which may occur in specific environments. The compositions of the cooling gases which decarburize the material have been determined; they are to be avoided during reactor operation

  16. Recognition structure of semipalatinsk residents caused by nuclear explosion tests

    International Nuclear Information System (INIS)

    Hirabayashi, Kyoko; Satoh, Kenichi; Ohtaki, Megu; Muldagaliyev, T.; Apsalikov, K.; Kawano, Noriyuki

    2012-01-01

    Authors' team of Hiroshima University and Scientific Research Institute of Radiation Medicine and Ecology (Kazakhstan) has been investigating the health state, exposure route, contents and mental effect of nuclear explosion tests of Semipalatinsk residents through their witness and questionnaire since 2002, to elucidate the humanistic damage of nuclear tests. Reported here is the recognition structure in the title statistically analyzed with use of frequently spoken words in the witness. The audit was performed in 2002-2007 to 994 residents who had experienced ground explosion tests during the period from 1949 to 1962 and were living in 26 villages near the old test site. Asked questions concerning nuclear tests involved such items as still unforgettable matters, dreadful events, regretting things, thought about the test, requests; and matters about themselves, their family, close friends and anything. The frequency of the test site-related words heard in the interview were analyzed with hierarchical clustering and multi-dimensional scaling with a statistic software R for computation and MeCab for morphological analysis. Residents' recognition was found to be of two structures of memory at explosion tests and anger/dissatisfaction/anxiety to the present state. The former contained the frequent words of mushroom cloud, flash, blast, ground tremble and outdoor evacuation, and the latter, mostly anxiety about health of themselves and family. Thus residents have had to be confronted with uneasiness of their health even 20 years after the closure of the test site. (T.T.)

  17. 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.

  18. Vertebral stabilization using positively threaded profile pins and polymethylmethacrylate, with or without laminectomy, for spinal canal stenosis and vertebral instability caused by congenital thoracic vertebral anomalies.

    Science.gov (United States)

    Aikawa, Takeshi; Kanazono, Shinichi; Yoshigae, Yuki; Sharp, Nicholas J H; Muñana, Karen R

    2007-07-01

    To describe diagnostic findings, surgical technique, and outcome in dogs with thoracic spinal canal stenosis and vertebral instability secondary to congenital vertebral anomalies. Retrospective clinical study. Dogs (n=9) with thoracic spinal canal stenosis. Medical records (1995-1996; 2000-2006) of 9 dogs with a myelographic diagnosis of spinal canal stenosis and/or vertebral instability secondary to congenital vertebral anomaly that were surgically managed by vertebral stabilization with or without laminectomy were reviewed. Data on pre- and postoperative neurologic status, diagnostic findings, surgical techniques, and outcomes were retrieved. Follow-up evaluations were performed at 1, 2, and 6 months. Long-term outcome was assessed by means of clinical examination or owner telephone interviews. Spinal cord compression was confirmed by myelography, and in 2 dogs, dynamic compression by stress myelography. Eight dogs regained the ability to ambulate postoperatively. One dog with a partial recovery regained voluntary movement but did not become ambulatory. Spinal cord injury secondary to congenital vertebral anomaly may have a good outcome when treated by vertebral stabilization with or without laminectomy. Adequate stabilization of the vertebrae and improved neurologic outcome were achieved in most dogs. Vertebral stabilization using positively threaded profile pins and polymethylmethacrylate with or without laminectomy is an effective treatment for spinal canal stenosis and vertebral instability secondary to congenital thoracic vertebral anomalies.

  19. Multifragmentation: Surface instabilities or statistical decay

    International Nuclear Information System (INIS)

    Moretto, L.G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G.J.

    1992-11-01

    Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space

  20. Multifragmentation: surface instabilities or statistical decay?

    International Nuclear Information System (INIS)

    Moretto, L.G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G.J.

    1993-01-01

    Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space. (author)

  1. Controlling chaos in the current-driven ion acoustic instability

    International Nuclear Information System (INIS)

    Fukuyama, T.; Taniguchi, K.; Kawai, Y.

    2002-01-01

    Control of intermittent chaos caused by the current-driven ion acoustic instability is attempted and the controlling mechanism is investigated. When a small negative dc voltage is applied to the chaotic system as a perturbation, the system changes from a chaotic state to a periodic state while maintaining the instability, indicating that the chaotic state caused by the ion acoustic instability is well controlled by applying a small negative dc voltage. A hysteresis structure is observed on the V-I curve of the mesh grid to which the negative dc voltage to control is applied. Furthermore, when a negative dc voltage is applied to the state which shows a laminar structure existing under same experimental conditions, the system becomes chaotic via a bifurcation. Driven-chaos is excited when a negative dc voltage is applied to the laminar state. Applying a small negative dc voltage leads to controlling intermittent chaos while exciting driven-chaos

  2. Assessing Whether Oil Dependency in Venezuela Contributes to National Instability

    Directory of Open Access Journals (Sweden)

    Adam Kott

    2012-08-01

    Full Text Available The focus of this article is on what role, if any, oil has on Venezuela's instability. When trying to explain why a resource-rich country experiences slow or negative growth, experts often point to the resource curse. The following pages explore the traditional theory behind the resource curse as well as alternative perspectives to this theory such as ownership structure and the correlation between oil prices and democracy. This article also explores the various forms of instability within Venezuela and their causes. Finally, the article looks at President Hugo Chavez's political and economic policies as well as the stagnation of the state oil company, Petroleos de Venezuela (PDVSA. This article dispels the myth that the resource curse is the source of destabilization in many resource dependent countries. Rather than a cause of instability, this phenomenon is a symptom of a much larger problem that is largely structural.

  3. Instabilities and soot formation in spherically expanding, high pressure, rich, iso-octane-air flames

    International Nuclear Information System (INIS)

    Lockett, R D

    2006-01-01

    Flame instabilities, cellular structures and soot formed in high pressure, rich, spherically expanding iso-octane-air flames have been studied experimentally using high speed Schlieren cinematography, OH fluorescence, Mie scattering and laser induced incandescence. Cellular structures with two wavelength ranges developed on the flame surface. The larger wavelength cellular structure was produced by the Landau-Darrieus hydrodynamic instability, while the short wavelength cellular structure was produced by the thermal-diffusive instability. Large negative curvature in the short wavelength cusps caused local flame quenching and fracture of the flame surface. In rich flames with equivalence ratio φ > 1.8, soot was formed in a honeycomb-like structure behind flame cracks associated with the large wavelength cellular structure induced by the hydrodynamic instability. The formation of soot precursors through low temperature pyrolysis was suggested as a suitable mechanism for the initiation of soot formation behind the large wavelength flame cracks

  4. Instabilities and soot formation in spherically expanding, high pressure, rich, iso-octane-air flames

    Energy Technology Data Exchange (ETDEWEB)

    Lockett, R D [School of Engineering and Mathematical Sciences, City University, Northampton Square, London EC1V OHB (United Kingdom)

    2006-07-15

    Flame instabilities, cellular structures and soot formed in high pressure, rich, spherically expanding iso-octane-air flames have been studied experimentally using high speed Schlieren cinematography, OH fluorescence, Mie scattering and laser induced incandescence. Cellular structures with two wavelength ranges developed on the flame surface. The larger wavelength cellular structure was produced by the Landau-Darrieus hydrodynamic instability, while the short wavelength cellular structure was produced by the thermal-diffusive instability. Large negative curvature in the short wavelength cusps caused local flame quenching and fracture of the flame surface. In rich flames with equivalence ratio {phi} > 1.8, soot was formed in a honeycomb-like structure behind flame cracks associated with the large wavelength cellular structure induced by the hydrodynamic instability. The formation of soot precursors through low temperature pyrolysis was suggested as a suitable mechanism for the initiation of soot formation behind the large wavelength flame cracks.

  5. Dynamic ultrasound of peroneal tendon instability.

    Science.gov (United States)

    Pesquer, Lionel; Guillo, Stéphane; Poussange, Nicolas; Pele, Eric; Meyer, Philippe; Dallaudière, Benjamin

    2016-07-01

    Ankle snapping may be caused by peroneal tendon instability. Anterior instability occurs after traumatic superior peroneal retinaculum injury, whereas peroneal tendon intrasheath subluxation is atraumatic. Whereas subluxation is mainly dynamic, ultrasound allows for the diagnosis and classification of peroneal instability because it allows for real-time exploration. The purpose of this review is to describe the anatomic and physiologic bases for peroneal instability and to heighten the role of dynamic ultrasound in the diagnosis of snapping.

  6. Simulation, measurement, and mitigation of beam instability caused by the kicker impedance in the 3-GeV rapid cycling synchrotron at the Japan Proton Accelerator Research Complex

    Science.gov (United States)

    Saha, P. K.; Shobuda, Y.; Hotchi, H.; Harada, H.; Hayashi, N.; Kinsho, M.; Tamura, F.; Tani, N.; Yamamoto, M.; Watanabe, Y.; Chin, Yong Ho; Holmes, J. A.

    2018-02-01

    The transverse impedance of eight extraction pulsed kicker magnets is a strong beam instability source in the 3-GeV rapid cycling synchrotron (RCS) at the Japan Proton Accelerator Research Complex. Significant beam instability occurs even at half of the designed 1 MW beam power when the chromaticity (ξ ) is fully corrected for the entire acceleration cycle by using ac sextupole (SX) fields. However, if ξ is fully corrected only at the injection energy by using dc SX fields, the beam is stable. In order to study realistic beam instability scenarios, including the effect of space charge and to determine practical measures to accomplish 1 MW beam power, we enhance the orbit particle tracking code to incorporate all realistic time-dependent machine parameters, including the time dependence of the impedance itself. The beam stability properties beyond 0.5 MW beam power are found to be very sensitive to a number of parameters in both simulations and measurements. In order to stabilize a beam at 1 MW beam power, two practical measures based on detailed and systematic simulation studies are determined, namely, (i) proper manipulation of the betatron tunes during acceleration and (ii) reduction of the dc SX field to reduce the ξ correction even at injection. The simulation results are well reproduced by measurements, and, as a consequence, an acceleration to 1 MW beam power is successfully demonstrated. In this paper, details of the orbit simulation and the corresponding experimental results up to 1 MW of beam power are presented. To further increase the RCS beam power, beam stability issues and possible measures beyond 1 MW beam power are also considered.

  7. Hemodynamic Instability after Low-Energy Thigh Contusion Caused by Injury to the Femoral Artery: A Case Report and Literature Review

    Directory of Open Access Journals (Sweden)

    Juan Miguel Rodríguez-Roiz

    2016-01-01

    Full Text Available Acute vascular injuries have been described in relation to high-energy trauma accidents or in patients undergoing surgery in the femoral area. We describe a healthy patient who sustained a direct, low-energy contusion in the thigh and presented haemodynamic instability. Arteriography was used to locate the point of bleeding, and embolisation and vessel occlusion were carried out to stop the haemorrhage. The genetic study identified the COL3A1 gene mutation; accordingly, the patient was diagnosed with the Ehlers-Danlos syndrome type IV (vascular type.

  8. Fluid-structure interaction analysis of a water pool under loading caused by steam injection

    International Nuclear Information System (INIS)

    Timperi, A.; Paettikangas, T.; Niemi, J.; Ilvonen, M.

    2006-04-01

    CFD and structural analysis codes. MpCCI 3.0 was used for coupling Fluent CFD code with ABAQUS FE code. ES-FSI was used for coupling Star-CD CFD code with ABAQUS. FSI analyses, in which the calculation was carried out entirely in ABAQUS, were also performed. In this case, acoustic elements were used for the fluid and the acoustic and structural domains were coupled. FSI calculations were performed for simple test cases and for a test pool at Lappeenranta University of Technology. The Method of Images was studied as an alternative method for the analyses of the pool. Particularly, the determination of pressure source for the method was studied. Earlier work carried out with the homogenous two-phase model was continued by testing the model with Fluent. Calculation of condensation of steam in a water pool was tested with a new implementation. The two-directionally coupled simulations of the pool with MpCCI and ES-FSI were found to be numerically instable. It was concluded that an implicit coupling method may have to be used in order to avoid the instability. Calculations of the pool were finally performed by using one directional coupling. In the simulations with MpCCI, the incompressible and compressible VOF models of Fluent were used. With ES-FSI, the incompressible VOF model of Star-CD was used for modelling the beginning of a steam injection experiment. The magnitudes of pressure and stress peaks in the simulation and experiment were of comparable size. Otherwise, however, differences between the simulation and experiment were large due to the simplifications used in the simulation. Results obtained with the acoustic-structural FE analyses were compared to analytical and experimental results. The results indicated that the coupled acoustic-structural analysis can be used for calculating the coupled Eigenmodes of BWR pressure suppression pools. (au)

  9. Fluid-structure interaction analysis of a water pool under loading caused by steam injection

    Energy Technology Data Exchange (ETDEWEB)

    Timperi, A.; Paettikangas, T.; Niemi, J.; Ilvonen, M. [VTT Technical Researc Centre of Finland (Finland)

    2006-04-15

    CFD and structural analysis codes. MpCCI 3.0 was used for coupling Fluent CFD code with ABAQUS FE code. ES-FSI was used for coupling Star-CD CFD code with ABAQUS. FSI analyses, in which the calculation was carried out entirely in ABAQUS, were also performed. In this case, acoustic elements were used for the fluid and the acoustic and structural domains were coupled. FSI calculations were performed for simple test cases and for a test pool at Lappeenranta University of Technology. The Method of Images was studied as an alternative method for the analyses of the pool. Particularly, the determination of pressure source for the method was studied. Earlier work carried out with the homogenous two-phase model was continued by testing the model with Fluent. Calculation of condensation of steam in a water pool was tested with a new implementation. The two-directionally coupled simulations of the pool with MpCCI and ES-FSI were found to be numerically instable. It was concluded that an implicit coupling method may have to be used in order to avoid the instability. Calculations of the pool were finally performed by using one directional coupling. In the simulations with MpCCI, the incompressible and compressible VOF models of Fluent were used. With ES-FSI, the incompressible VOF model of Star-CD was used for modelling the beginning of a steam injection experiment. The magnitudes of pressure and stress peaks in the simulation and experiment were of comparable size. Otherwise, however, differences between the simulation and experiment were large due to the simplifications used in the simulation. Results obtained with the acoustic-structural FE analyses were compared to analytical and experimental results. The results indicated that the coupled acoustic-structural analysis can be used for calculating the coupled Eigenmodes of BWR pressure suppression pools. (au)

  10. Suppression of Genomic Instabilities Caused by Chromosome Mis-segregation: A Perspective From Studying BubR1 and Sgo1

    Science.gov (United States)

    Dai, Wei

    2013-01-01

    Aneuploidy is a major manifestation of chromosomal instability, which is defined as a numerical abnormality of chromosomes in diploid cells. It is highly prevalent in a variety of human malignancies. Increased chromosomal instability is the major driving force for tumor development and progression. To suppress genomic stability during cell division, eukaryotic cells have evolved important molecular mechanisms, commonly referred to as checkpoints. The spindle checkpoint ensures that cells with defective mitotic spindles or a defective interaction between the spindles and kinetochores do not initiate chromosomal segregation during mitosis. Extensive studies have identified and characterized more than a dozen genes that play important roles in the regulation of the spindle checkpoint in mammalian cells. During the past decade, we have carried out extensive investigation of the role of BubR1 (Bub1-related kinase) and Sgo1 (shugoshin 1), two important gene products that safeguard accurate chromosome segregation during mitosis. This mini-review summarizes our studies, as well as those by other researchers in the field, on the functions of these two checkpoint proteins and their molecular regulation during mitosis. Further elucidation of the molecular mechanisms of the spindle checkpoint regulation has the potential to identify important mitotic targets for rational anticancer drug design. PMID:20040454

  11. Suppression of Genomic Instabilities Caused by Chromosome Mis-segregation: A Perspective From Studying BubR1 and Sgo1

    Directory of Open Access Journals (Sweden)

    Wei Dai

    2009-12-01

    Full Text Available Aneuploidy is a major manifestation of chromosomal instability, which is defined as a numerical abnormality of chromosomes in diploid cells. It is highly prevalent in a variety of human malignancies. Increased chromosomal instability is the major driving force for tumor development and progression. To suppress genomic stability during cell division, eukaryotic cells have evolved important molecular mechanisms, commonly referred to as checkpoints. The spindle checkpoint ensures that cells with defective mitotic spindles or a defective interaction between the spindles and kinetochores do not initiate chromosomal segregation during mitosis. Extensive studies have identified and characterized more than a dozen genes that play important roles in the regulation of the spindle checkpoint in mammalian cells. During the past decade, we have carried out extensive investigation of the role of BubR1 (Bub1-related kinase and Sgo1 (shugoshin 1, two important gene products that safeguard accurate chromosome segregation during mitosis. This mini-review summarizes our studies, as well as those by other researchers in the field, on the functions of these two checkpoint proteins and their molecular regulation during mitosis. Further elucidation of the molecular mechanisms of the spindle checkpoint regulation has the potential to identify important mitotic targets for rational anticancer drug design.

  12. Fluctuations and Instability in Sedimentation

    KAUST Repository

    Guazzelli, É lisabeth; Hinch, John

    2011-01-01

    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

  13. Trisomy 21 and facial developmental instability.

    Science.gov (United States)

    Starbuck, John M; Cole, Theodore M; Reeves, Roger H; Richtsmeier, Joan T

    2013-05-01

    The most common live-born human aneuploidy is trisomy 21, which causes Down syndrome (DS). Dosage imbalance of genes on chromosome 21 (Hsa21) affects complex gene-regulatory interactions and alters development to produce a wide range of phenotypes, including characteristic facial dysmorphology. Little is known about how trisomy 21 alters craniofacial morphogenesis to create this characteristic appearance. Proponents of the "amplified developmental instability" hypothesis argue that trisomy 21 causes a generalized genetic imbalance that disrupts evolutionarily conserved developmental pathways by decreasing developmental homeostasis and precision throughout development. Based on this model, we test the hypothesis that DS faces exhibit increased developmental instability relative to euploid individuals. Developmental instability was assessed by a statistical analysis of fluctuating asymmetry. We compared the magnitude and patterns of fluctuating asymmetry among siblings using three-dimensional coordinate locations of 20 anatomic landmarks collected from facial surface reconstructions in four age-matched samples ranging from 4 to 12 years: (1) DS individuals (n = 55); (2) biological siblings of DS individuals (n = 55); 3) and 4) two samples of typically developing individuals (n = 55 for each sample), who are euploid siblings and age-matched to the DS individuals and their euploid siblings (samples 1 and 2). Identification in the DS sample of facial prominences exhibiting increased fluctuating asymmetry during facial morphogenesis provides evidence for increased developmental instability in DS faces. We found the highest developmental instability in facial structures derived from the mandibular prominence and lowest in facial regions derived from the frontal prominence. Copyright © 2013 Wiley Periodicals, Inc.

  14. THE SATURATION OF SASI BY PARASITIC INSTABILITIES

    International Nuclear Information System (INIS)

    Guilet, Jerome; Sato, Jun'ichi; Foglizzo, Thierry

    2010-01-01

    The standing accretion shock instability (SASI) is commonly believed to be responsible for large amplitude dipolar oscillations of the stalled shock during core collapse, potentially leading to an asymmetric supernovae explosion. The degree of asymmetry depends on the amplitude of SASI, but the nonlinear saturation mechanism has never been elucidated. We investigate the role of parasitic instabilities as a possible cause of nonlinear SASI saturation. As the shock oscillations create both vorticity and entropy gradients, we show that both Kelvin-Helmholtz and Rayleigh-Taylor types of instabilities are able to grow on a SASI mode if its amplitude is large enough. We obtain simple estimates of their growth rates, taking into account the effects of advection and entropy stratification. In the context of the advective-acoustic cycle, we use numerical simulations to demonstrate how the acoustic feedback can be decreased if a parasitic instability distorts the advected structure. The amplitude of the shock deformation is estimated analytically in this scenario. When applied to the set up of Fernandez and Thompson, this saturation mechanism is able to explain the dramatic decrease of the SASI power when both the nuclear dissociation energy and the cooling rate are varied. Our results open new perspectives for anticipating the effect, on the SASI amplitude, of the physical ingredients involved in the modeling of the collapsing star.

  15. Local damage to reinforced concrete structures caused by impact of aircraft engine missiles. Pt. 1

    International Nuclear Information System (INIS)

    Sugano, T.; Tsubota, H.; Kasai, Y.; Koshika, N.; Ohnuma, H.; Von Riesemann, W.A.; Bickel, D.C.; Parks, M.B.

    1993-01-01

    Structural damage induced by an aircraft crashing into a reinforced concrete structure includes local damage caused by the deformable engines, and global damage caused by the entire aircraft. Local damage to the target may consist of spalling of concrete from its front face together with missile penetration into it, scabbing of concrete from its rear face, and perforation of missile through it. Until now, local damage to concrete structures has been mainly evaluated by rigid missile impact tests. Past research work regarding local damage caused by impact of deformable missiles has been limited. This paper presents the results of a series of impact tests of small-, intermediate-, and full-scale engine models into reinforced concrete panels. The purpose of the tests was to determine the local damage to a reinforced concrete structure caused by the impact of a deformable aircraft engine. (orig.)

  16. Cases of coupled vibrations and prametric instability in rotating machines

    OpenAIRE

    Luneno, Jean-Claude

    2012-01-01

    The principal task in this research project was to analyse the causes and consequences of coupled vibrations and parametric instability in hydropower rotors; where both horizontal and vertical machines are involved. Vibration is a well-known undesirable behavior of dynamical systems characterised by persistent periodic, quasi-periodic or chaotic motions. Vibrations generate noise and cause fatigue, which initiates cracks in mechanical structures. Motions coupling can in some cases augment the...

  17. A theorical experimental comparison of the buckling caused by fluid structure interaction during a seismic load

    International Nuclear Information System (INIS)

    Aillaud, P.; Buland, P.; Combescure, A.; Queval, J.C.; Garuti, G.

    1983-08-01

    The buckling of shells subjected to seismic type of loads is not very well known. To study this type of phenomenon we have performed theorical and experimental investigations on structures consisting of two shells separed by a thin fluid layer, and submitted to a seismic type of load. The objectives of these investigations are the following: study the coupling between buckling modes and vibrations modes and buckling of the effects of this coupling on the level of the pressure; study of the appearance on such structures of dynamic instabilities processes; qualification of computer codes of the CEASEMT system; and, qualification or criticism of the methodology used in the design based on a ''static equivalent'' idea. The experiments are made on two types of structures: spherical and cylindrical shells. The load applied on the shells consists of a permanent pressure and of a dynamic pressure due to fluid structure interaction. The systeme is put on the vibrating table and excitation is vertical for the hemispherical case, and horizontal for the cylindrical cases. Six models of each type are tested, with sinusoidal excitation at resonance. The tests on the spherical shells are presented and compared with calculations. The correlation is good and the main results is, as predicted by numerical calculation, that if the sum of the permanent and oscillatory pressure is greater than the static buckling load, the shells buckle. This results validates the static methodology. The tests on the cylindrical tanks will be exploited by the end of the year and presented in this paper

  18. Instability following total knee arthroplasty.

    Science.gov (United States)

    Rodriguez-Merchan, E Carlos

    2011-10-01

    Background Knee prosthesis instability (KPI) is a frequent cause of failure of total knee arthroplasty. Moreover, the degree of constraint required to achieve immediate and long-term stability in total knee arthroplasty (TKA) is frequently debated. Questions This review aims to define the problem, analyze risk factors, and review strategies for prevention and treatment of KPI. Methods A PubMed (MEDLINE) search of the years 2000 to 2010 was performed using two key words: TKA and instability. One hundred and sixty-five initial articles were identified. The most important (17) articles as judged by the author were selected for this review. The main criteria for selection were that the articles addressed and provided solutions to the diagnosis and treatment of KPI. Results Patient-related risk factors predisposing to post-operative instability include deformity requiring a large surgical correction and aggressive ligament release, general or regional neuromuscular pathology, and hip or foot deformities. KPI can be prevented in most cases with appropriate selection of implants and good surgical technique. When ligament instability is anticipated post-operatively, the need for implants with a greater degree of constraint should be anticipated. In patients without significant varus or valgus malalignment and without significant flexion contracture, the posterior cruciate ligament (PCL) can be retained. However, the PCL should be sacrificed when deformity exists particularly in patients with rheumatoid arthritis, previous patellectomy, previous high tibial osteotomy or distal femoral osteotomy, and posttraumatic osteoarthritis with disruption of the PCL. In most cases, KPI requires revision surgery. Successful outcomes can only be obtained if the cause of KPI is identified and addressed. Conclusions Instability following TKA is a common cause of the need for revision. Typically, knees with deformity, rheumatoid arthritis, previous patellectomy or high tibial osteotomy, and

  19. Examining the evolution towards turbulence through spatio-temporal analysis of multi-dimensional structures formed by instability growth along a shear layer

    Science.gov (United States)

    Merritt, Elizabeth; Doss, Forrest; Loomis, Eric; Flippo, Kirk; Devolder, Barbara; Welser-Sherrill, Leslie; Fincke, James; Kline, John

    2014-10-01

    The counter-propagating shear campaign is examining instability growth and its transition to turbulence relevant to mix in ICF capsules. Experimental platforms on both OMEGA and NIF use anti-symmetric flows about a shear interface to examine isolated Kelvin-Helmholtz instability growth. Measurements of interface (an Al or Ti tracer layer) dynamics are used to benchmark the LANL RAGE hydrocode with BHR turbulence model. The tracer layer does not expand uniformly, but breaks up into multi-dimensional structures that are initially quasi-2D due to the target geometry. We are developing techniques to analyze the multi-D structure growth along the tracer surface with a focus on characterizing the time-dependent structures' spectrum of scales in order to appraise a transition to turbulence in the system and potentially provide tighter constraints on initialization schemes for the BHR model. To this end, we use a wavelet based analysis to diagnose single-time radiographs of the tracer layer surface (w/low and amplified roughness for random noise seeding) with observed spatially non-repetitive features, in order to identify spatial and temporal trends in radiographs taken at different times across several experimental shots. This work conducted under the auspices of the U.S. Department of Energy by LANL under Contract DE-AC52-06NA25396.

  20. Hidden spondylolisthesis: unrecognized cause of low back pain? Prospective study about the use of dynamic projections in standing and recumbent position for the individuation of lumbar instability

    International Nuclear Information System (INIS)

    Landi, Alessandro; Gregori, Fabrizio; Marotta, Nicola; Donnarumma, Pasquale; Delfini, Roberto

    2015-01-01

    Dynamic X-rays (DXR) are widely recognized as an effective method to detect lumbar instability (LI). They are usually performed with the patient in standing position (SDXR). In our opinion, standing position inhibits micromovements of the lumbar segment interested by the listhesis, thanks to paravertebral muscles antalgic contraction and augmented tone. We aim to demonstrate that DXR in recumbent position (RDXR), reducing the action of paravertebral muscles, can discover hypermovements not evidenced in SDXR. Between January 2011 and January 2013, we studied 200 consecutive patients with lumbar degenerative disease with MRI, SDXR, and RDXR. We aimed to find a correlation between low back or radicular pain and the presence of a spondylolisthesis not showed by the SDXR, but showed by the RDXR. We analysed 200 patients: of the 133 not pathologic in SDXR, 43 patients (32.3 %) showed an hypermovement in RDXR (p = 0.0001) without any significant correlation between hidden listhesis and age, sex, or level involved. The aim of our study is to determine whether in patients with lumbalgy without evidence of listhesis in SDXR, pain can be attributed to a faccettal syndrome or to a spondylolisthesis. Consequence of pain is augmented muscular tone of the paravertebral musculature, particularly in standing position. Augmented muscular tone tries to inhibit the pain generator, attempting to limit the slippage of the involved segment. In patients examined in RDXR, the tone of paravertebral musculature is reduced, showing the hidden spondylolisthesis. (orig.)

  1. Hidden spondylolisthesis: unrecognized cause of low back pain? Prospective study about the use of dynamic projections in standing and recumbent position for the individuation of lumbar instability

    Energy Technology Data Exchange (ETDEWEB)

    Landi, Alessandro; Gregori, Fabrizio; Marotta, Nicola; Donnarumma, Pasquale; Delfini, Roberto [University of Rome - Policlinico Umberto I, Department of Neurology and Psychiatry, Division of Neurosurgery, Rome (Italy)

    2015-03-26

    Dynamic X-rays (DXR) are widely recognized as an effective method to detect lumbar instability (LI). They are usually performed with the patient in standing position (SDXR). In our opinion, standing position inhibits micromovements of the lumbar segment interested by the listhesis, thanks to paravertebral muscles antalgic contraction and augmented tone. We aim to demonstrate that DXR in recumbent position (RDXR), reducing the action of paravertebral muscles, can discover hypermovements not evidenced in SDXR. Between January 2011 and January 2013, we studied 200 consecutive patients with lumbar degenerative disease with MRI, SDXR, and RDXR. We aimed to find a correlation between low back or radicular pain and the presence of a spondylolisthesis not showed by the SDXR, but showed by the RDXR. We analysed 200 patients: of the 133 not pathologic in SDXR, 43 patients (32.3 %) showed an hypermovement in RDXR (p = 0.0001) without any significant correlation between hidden listhesis and age, sex, or level involved. The aim of our study is to determine whether in patients with lumbalgy without evidence of listhesis in SDXR, pain can be attributed to a faccettal syndrome or to a spondylolisthesis. Consequence of pain is augmented muscular tone of the paravertebral musculature, particularly in standing position. Augmented muscular tone tries to inhibit the pain generator, attempting to limit the slippage of the involved segment. In patients examined in RDXR, the tone of paravertebral musculature is reduced, showing the hidden spondylolisthesis. (orig.)

  2. Research Review: Structural Language in Autistic Spectrum Disorder--Characteristics and Causes

    Science.gov (United States)

    Boucher, Jill

    2012-01-01

    Background: Structural language anomalies or impairments in autistic spectrum disorder (ASD) are theoretically and practically important, although underrecognised as such. This review aims to highlight the ubiquitousness of structural language anomalies and impairments in ASD, and to stimulate investigation of their immediate causes and…

  3. Using thin metal layers on composite structures for shielding the electromagnetic pulse caused by nearby lightning

    NARCIS (Netherlands)

    Blaj, M.A.; Buesink, Frederik Johannes Karel; Damstra, G.C.; Leferink, Frank Bernardus Johannes

    2011-01-01

    Electronic systems in composite structures could be vulnerable to the (dominant magnetic) field caused by a lightning strike, because only thin layers of metal can be used on composite structures. Thin layers result in a very low shielding effectiveness against magnetic fields. Many experiments

  4. Nonlinear evolution of single spike in Richtmyer-Meshkov instability

    International Nuclear Information System (INIS)

    Fukuda, Y.; Nishihara, K.; Wouchuk, J.G.

    2000-01-01

    Nonlinear evolution of single spike structure and vortex in the Richtmyer-Meshkov instability is investigated with the use of a two-dimensional hydrodynamic code. It is shown that singularity appears in the vorticity left by transmitted and reflected shocks at a corrugated interface. This singularity results in opposite sign of vorticity along the interface that causes double spiral structure of the spike. (authors)

  5. Orphans and political instability.

    Science.gov (United States)

    Breuning, Marijke; Ishiyama, John

    2011-01-01

    This study investigates the security implications of growing orphan populations, particularly in Sub-Saharan Africa. Little has been written about the security implications of this especially vulnerable group of children. Are growing orphan populations associated with increases in political instability as has been suggested? Using data from several sources, we employ regression analysis to test whether Sub-Saharan African countries with larger proportions of orphans and those with increasing orphan populations experience higher rates of political instability. We find that the increase in the orphan population is related to an increasing incidence of civil conflict, but do not find a similar relationship for the proportion of orphans. In addition, we find that the causes of orphanhood matter. We conclude that increases in orphan populations (rather than simple proportions) are destabilizing. We suggest possible avenues for mediating the security risks posed by growing orphan populations.

  6. Imaging of patellofemoral instability

    International Nuclear Information System (INIS)

    Waldt, S.; Rummeny, E.J.

    2012-01-01

    Patellofemoral instability remains a diagnostic and therapeutic challenge due to its multifactorial genesis. The purpose of imaging is to systematically analyze predisposing factors, such as trochlear dysplasia, patella alta, tibial tuberosity-trochlear groove (TT-TG) distance, rotational deformities of the lower limb and patellar tilt. In order to evaluate anatomical abnormalities with a sufficient diagnostic accuracy, standardized measurement methods and implementation of various imaging modalities are necessary. Diagnosis of acute and often overlooked lateral patellar dislocation can be established with magnetic resonance imaging (MRI) because of its characteristic patterns of injury. Damage to the medial patellofemoral ligament (MPFL) has a significance just as high as the predisposing risk factors in relation to the cause of chronic instability. (orig.) [de

  7. Thermo-Structural Response Caused by Structure Gap and Gap Design for Solid Rocket Motor Nozzles

    Directory of Open Access Journals (Sweden)

    Lin Sun

    2016-06-01

    Full Text Available The thermo-structural response of solid rocket motor nozzles is widely investigated in the design of modern rockets, and many factors related to the material properties have been considered. However, little work has been done to evaluate the effects of structure gaps on the generation of flame leaks. In this paper, a numerical simulation was performed by the finite element method to study the thermo-structural response of a typical nozzle with consideration of the structure gap. Initial boundary conditions for thermo-structural simulation were defined by a quasi-1D model, and then coupled simulations of different gap size matching modes were conducted. It was found that frictional interface treatment could efficiently reduce the stress level. Based on the defined flame leak criteria, gap size optimization was carried out, and the best gap matching mode was determined for designing the nozzle. Testing experiment indicated that the simulation results from the proposed method agreed well with the experimental results. It is believed that the simulation method is effective for investigating thermo-structural responses, as well as designing proper gaps for solid rocket motor nozzles.

  8. Cavitation instabilities in hydraulic machines

    International Nuclear Information System (INIS)

    Tsujimoto, Y

    2013-01-01

    Cavitation instabilities in hydraulic machines, hydro turbines and turbopump inducers, are reviewed focusing on the cause of instabilities. One-dimensional model of hydro turbine system shows that the overload surge is caused by the diffuser effect of the draft tube. Experiments show that this effect also causes the surge mode oscillations at part load. One dimensional model of a cavitating turbopump inducer shows that the mass flow gain factor, representing the cavity volume increase caused by the incidence angle increase is the cause of cavitation surge and rotating cavitation. Two dimensional model of a cavitating turbopump inducer shows that various modes of cavitation instabilities start to occur when the cavity length becomes about 65% of the blade spacing. This is caused by the interaction of the local flow near the cavity trailing edge with the leading edge of the next blade. It was shown by a 3D CFD that this is true also for real cases with tip cavitation. In all cases, it was shown that cavitation instabilities are caused by the fundamental characteristics of cavities that the cavity volume increases with the decrease of ambient pressure or the increase of the incidence angle

  9. Owner and Contractor Perceptions Toward Factors Causing Delays in Structural and Finishing Works

    Directory of Open Access Journals (Sweden)

    Loanata V.R.

    2010-01-01

    Full Text Available A construction project comprises of a number of work packages, which are subjected to delays. These delays may be caused by many on-site factors. The aim of this research is to represent owner and contractors perceptions towards delay factors that frequently occur in structural and finishing works. Data for analysis were gathered by distributing questionnaire. A total of 198 sets of questionnaire were gathered and used for subsequent analyses. In general, design changes during construction are perceived by respondents as the most frequent factor to cause delay in all structural and finishing works. The results also show that there are a number of differences between owner’s and contractor’s perceptions towards the occurrences of the factors. Whilst most contractors concern that information factors related to project design and scope frequently causing delays in construction works, owners consider many contractor originated factors, as most frequent delay causes.

  10. Testing and diagnosis of the cause of increased vibration of the fan plant's support structure

    Directory of Open Access Journals (Sweden)

    Varju Đerđ

    2015-01-01

    Full Text Available This paper presents a procedure of determining the causes of increased vibration of a fan plant and its support structure in the PUC 'Subotička toplana'. Excessive vibrations were observed following the installation of the frequency converter, thus a methodological approach of testing-analysis-diagnosis has been applied. Based on the definition of the causes of this problem, the paper also suggests possible repair procedures.

  11. Electrostatic instabilities and nonlinear structures of low-frequency waves in nonuniform electron-positron-ion plasmas with shear flow

    International Nuclear Information System (INIS)

    Mirza, Arshad M.; Hasan, Asma; Azeem, M.; Saleem, H.

    2003-01-01

    It is found that the low-frequency ion acoustic and electrostatic drift waves can become unstable in uniform electron-ion and electron-positron-ion plasmas due to the ion shear flow. In a collisional plasma a drift-dissipative instability can also take place. In the presence of collisions the temporal behavior of nonlinear drift-dissipative mode can be represented in the form of well-known Lorenz and Stenflo type equations that admit chaotic trajectories. On the other hand, a quasi-stationary solution of the mode coupling equations can be represented in the form of monopolar vortex. The results of the present investigation can be helpful in understanding electrostatic turbulence and wave phenomena in laboratory and astrophysical plasmas

  12. Threshold of decay instability in an inhomogeneous plasma (Leningrad 1973)

    International Nuclear Information System (INIS)

    Piliia, A.D.

    It is shown that in a spatially inhomogeneous plasma there can exist an absolute decay instability with a threshold lower than that found earlier. This instability arises when two parametrically coupled waves have turning points inside the plasma layer. The cause of the instability is a positive inverse coupling, caused by a nonlinear conversion and a reflection of the waves

  13. Impaired skin capillary recruitment in essential hypertension is caused by both functional and structural capillary rarefaction

    NARCIS (Netherlands)

    Serne, EH; Gans, ROB; ter Maaten, JC; Tangelder, GJ; Donker, AJM; Stehouwer, CDA

    Capillary rarefaction occurs in many tissues in patients with essential hypertension and may contribute to an increased vascular resistance and impaired muscle metabolism. Rarefaction may be caused by a structural (anatomic) absence of capillaries, functional nonperfusion, or both. The aim of this

  14. Structural changes of organic solids caused by irradiation: raman study at very low temperatures

    International Nuclear Information System (INIS)

    Hase, Hirotomo; Ishioka, Kunie; Miyatake, Yoko.

    1995-01-01

    In this paper we first describe a simple liquid helium cryostat and a device of making and mounting organic solid samples. We then present the Raman spectra for irradiated ethanol crystal that were obtained by using the new cryostat and demonstrate how the Raman method is useful for getting insight into structural changes of organic solids caused by irradiation. (J.P.N.)

  15. Phase instability and toughness change during high temperature exposure of various steels for the first wall structural materials of a fusion reactor

    International Nuclear Information System (INIS)

    Miyahara, K.; Shimoide, Y.

    1995-01-01

    The objective of the present research is to clarify the phase instability, particularly, the precipitation behavior of carbide and nitride during the long term aging in the non-irradiation state of the materials proposed for the first wall structural component of fusion reactors, such as a type 316 austenitic steel, its modified steels, ferritic heat resisting steels and reduced radio-activation materials. The effect of the precipitation behavior on the toughness is also investigated. It is noticed that the toughness was much deteriorated by the formation of large amounts of coarse carbides within grains and on grain boundaries during 2.88x10 4 ks (8000 h) aging at 873 K and that intergranular fracture occurred by the impact test at room temperature even in the type 316 steel. (orig.)

  16. Experimental investigation of two-dimensional critical surface structure, stimulated Raman scattering, and two-plasmon decay instability. Annual report, January 1, 1981-April 30, 1982

    International Nuclear Information System (INIS)

    Wong, A.Y.; Eggleston, D.L.; Tanikawa, T.; Qian, S.J.

    1982-11-01

    Experimental observations of the space and time evolution of resonantly enhanced electrostatic electric fields and plasma density in cylindrical geometry demonstrate the development of two-dimensional caviton structure when an initial density perturbation is imposed on the plasma in the direction perpendicular to the driver field. This two-dimensional structure is observed after the development of profile modification and grows on the ion time scale. The existence of a large azimuthal electric field component is an observational signature of two-dimensional structure. Enhanced electric field maxima are found to be azimuthally correlated with the density minima. Both the density cavities and electric field peaks exhibit increased azimuthal location with the growth of two-dimensional structure. The two-dimensional development exhibits a strong dependence on both perturbation wavenumber and driver power. The related theoretical literature is reviewed and numerical, analytical, and qualitative hybrid models for a driven, two-dimensional, inhomogeneous plasma are presented. Preliminary work is presented in the following additional areas: weak magnetic field effects on critical surface physics, optical measurements of fast electron production, two-dimensional effects in microwave-plasma interactions, Langmuir wave trapping, stimulated Raman scattering and two-plasmon decay instability

  17. Local damage to reinforced concrete structures caused by impact of aircraft engine missiles. Pt. 2

    International Nuclear Information System (INIS)

    Sugano, T.; Tsubota, H.; Kasai, Y.; Koshika, N.; Itoh, C.; Shirai, K.; Von Riesemann, W.A.; Bickel, D.C.; Parks, M.B.

    1993-01-01

    Three sets of impact tests, small-, intermediate-, and full-scale tests, have been executed to determine local damage to reinforced concrete structures caused by the impact of aircraft engine missiles. The results of the test program showed that (1) the use of the similarity law is appropriate, (2) suitable empirical formulas exist for predicting the local damage caused by rigid missiles, (3) reduction factors may be used for evaluating the reduction in local damage due to the deformability of the engines, (4) the reinforcement ratio has no effect on local damage, and (5) the test results could be adequately predicted using nonlinear response analysis. (orig.)

  18. Structural instability of sheath potential distribution and its possible implications for the L/H transition in tokamak plasmas

    International Nuclear Information System (INIS)

    Yoshida, Zensho; Yamada, Hiroshi.

    1988-07-01

    The Bohm equation of electrostatic potential distributions in one-dimensional plasmas has been studied for various Mach numbers and plasma potentials. Solvability and structural stability have been discussed using the Sagdeev potential. Implications of the structural stability for the L/H transitions in tokamak plasmas has been also discussed. (author)

  19. Structural consequences of amino acid substitutions causing Tay-Sachs disease.

    Science.gov (United States)

    Ohno, Kazuki; Saito, Seiji; Sugawara, Kanako; Sakuraba, Hitoshi

    2008-08-01

    To determine the structural changes in the alpha-subunit of beta-hexosaminidase due to amino acid substitutions causing Tay-Sachs disease, we built structural models of mutant alpha-subunits resulting from 33 missense mutations (24 infantile and 9 late-onset), and analyzed the influence of each amino acid replacement on the structure by calculating the number of atoms affected and determining the solvent-accessible surface area of the corresponding amino acid residue in the wild-type alpha-subunit. In the infantile Tay-Sachs group, the number of atoms influenced by a mutation was generally larger than that in the late-onset Tay-Sachs group in both the main chain and the side chain, and residues associated with the mutations found in the infantile Tay-Sachs group tended to be less solvent-accessible than those in the late-onset Tay-Sachs group. Furthermore, color imaging determined the distribution and degree of the structural changes caused by representative amino acid substitutions, and that there were also differences between the infantile and late-onset Tay-Sachs disease groups. Structural study is useful for elucidating the basis of Tay-Sachs disease.

  20. 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...... ulnar collateral ligament caused no laxity during the PST. Division of the lateral collateral ligament caused maximal laxity of 4 degrees and 23 degrees during forced PST in valgus and external rotation (supination), respectively. Cutting of the LCLC at the ulnar or the humeral insertion was necessary...... for any PST stressed elbow joint laxity to occur. Total division of the LCLC induced a maximal laxity of 7.9 degrees and 37 degrees during forced PST in valgus and external rotation (supination), respectively. This study suggests the lateral collateral ligament to be the primary soft tissue constraint...

  1. Structural changes in connective tissues caused by a moderate laser heating

    International Nuclear Information System (INIS)

    Bagratashvili, Viktor N; Bagratashvili, N V; Sviridov, A P; Shakh, G Sh; Ignat'eva, Natalia Yu; Lunin, Valery V; Grokhovskaya, T E; Averkiev, S V

    2002-01-01

    The structural changes in adipose and fibrous tissues caused by 2- and 3-W IR laser irradiation are studied by the methods of IR and Raman spectroscopy and differential scanning calorimetry. It is shown that heating of fibrous tissue samples to 50 0 C and adipose tissue samples to 75 0 C by IR laser radiation changes the supramolecular structure of their proteins and triacylglycerides, respectively, without the intramolecular bond breaking. Heating of fibrous tissue to 70 0 C and adipose tissue to 90 - 110 0 C leads to a partial reversible denaturation of proteins and to oxidation of fats.

  2. Anisotropic gravitational instability

    International Nuclear Information System (INIS)

    Polyachenko, V.L.; Fridman, A.M.

    1988-01-01

    Exact solutions of stability problems are obtained for two anisotropic gravitational systems of different geometries - a layer of finite thickness at rest and a rotating cylinder of finite radius. It is shown that the anisotropic gravitational instability which develops in both cases is of Jeans type. However, in contrast to the classical aperiodic Jeans instability, this instability is oscillatory. The physics of the anisotropic gravitational instability is investigated. It is shown that in a gravitating layer this instability is due, in particular, to excitation of previously unknown interchange-Jeans modes. In the cylinder, the oscillatory Jeans instability is associated with excitation of a rotational branch, this also being responsible for the beam gravitational instability. This is the reason why this instability and the anisotropic gravitational instability have so much in common

  3. Investigations of the changes in the bentonite structure caused by the different treatments

    OpenAIRE

    Stojiljković S.; Stamenković M.; Kostić D.; Miljković M.; Arsić B.; Savić I.; Savić I.

    2015-01-01

    The bentonite was treated in different ways and the changes in structure were monitored. Acid activation with sulphuric acid of investigated bentonite caused the increase in specific volume of micropore-mesopore. It was shown that activation by acid obtained at a constant temperature and constant period of time provides the possibility to obtain samples of bentonite of searched porosity only by changing the concentration of sulphuric and hydrochloric acid. ...

  4. Pearling Instabilities of a Viscoelastic Thread

    Science.gov (United States)

    Deblais, A.; Velikov, K. P.; Bonn, D.

    2018-05-01

    Pearling instabilities of slender viscoelastic threads have received much attention, but remain incompletely understood. We study the instabilities in polymer solutions subject to uniaxial elongational flow. Two distinctly different instabilites are observed: beads on a string and blistering. The beads-on-a-string structure arises from a capillary instability whereas the blistering instability has a different origin: it is due to a coupling between stress and polymer concentration. By varying the temperature to change the solution properties we elucidate the interplay between flow and phase separation.

  5. Analysis of beam acceleration and instability on TWRR accelerator structure in PNC by beam-cavity interaction

    Energy Technology Data Exchange (ETDEWEB)

    Toyama, Shin`ichi [Power Reactor and Nuclear Fuel Development Corp., Oarai, Ibaraki (Japan). Oarai Engineering Center

    1998-07-01

    It is important for high current accelerators to estimate the contribution of the space charge effect to keep the beam off its beak up (BBU). The CW electron linac is designed in order to study BBU experimentally. The design is primary on the consideration which type of accelerator structure is suitable to reduce the BBU threshold, and how to observe and control BBU when it appears. The contribution of beam charge for the acceleration characteristics is surveyed by means of the comparison between traveling wave and standing wave structures in this report. At first, the characteristics of both traveling wave and standing wave structures are calculated analytically and the conversion efficiency and accelerator gain are presented. The merits and drawbacks are also mentioned concerning with unit accelerator length. Next, the choice of RF frequency on energy conversion is mentioned as independent matter of the types of accelerator structure. After that, the characteristics of TWRR are described as the advanced accelerator structure compared with above structures. The effect of longitudinal induced field is estimated by means of the loss parameter. The result from the analysis shows that the unit accelerator length is 1 m to get high conversion ratio from RF to beam power and that the BBU for transverse component is small. Therefore, total BBU is expected small in the accelerator, for transverse BBU is already expected small in previous reports. (author)

  6. Delayed chromosomal instability induced by DNA damage

    International Nuclear Information System (INIS)

    Morgan, W.F.; Marder, B.A.; Day, J.P.

    1994-01-01

    Cellular exposure to DNA damaging agents rapidly results in a dose dependent increase in chromosomal breakage and gross structural chromosomal rearrangements. Over recent years, evidence has been accumulating indicating genomic instability can manifest multiple generations after cellular exposure to physical and chemical DNA damaging agents. Genomic instability manifests in the progeny of surviving cells, and has been implicated in mutation, gene application, cellular transformation, and cell killing. To investigate chromosome instability following DNA damage, we have used fluorescence in situ hybridization to detect chromosomal rearrangements in a human/hamster somatic hybrid cell line following exposure to ionizing radiation. Delayed chromosomal instability was detected when multiple populations of uniquely arranged metaphases were observed in clonal isolates raised from single cells surviving X-irradiation many generations after exposure. At higher radiation doses, chromosomal instability was observed in a relatively high frequency of surviving clones and, in general, those clones showed delayed chromosome instability also showed reduced survival as measured by colony forming ability

  7. 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.

  8. Simulations relevant to the beam instability in the foreshock

    Science.gov (United States)

    Cairns, I. H.; Nishikawa, K.-I.

    1989-01-01

    The results presently obtained from two-dimensional simulations of the reactive instability for Maxwellian beams and cutoff distributions are noted to be consistent with recent suggestions that electrons backstreaming into earth's foreshock have steep-sided cutoff distributions, which are initially unstable to the reactive instability, and that the back-reaction to the wave growth causes the instability to pass into its kinetic phase. It is demonstrated that the reactive instability is a bunching instability, and that the reactive instability saturates and passes over into the kinetic phase by particle trapping.

  9. An evaluation of the fluid-elastic instability for Intermediate Heat Exchanger of Prototype Sodium-cooled fast Reactor

    International Nuclear Information System (INIS)

    Cho, Jaehun; Kim, Sungkyun; Koo, Gyeonghoi

    2014-01-01

    The sodium-cooled fast reactor (SFR) module consists of the vessel, containment vessel, head, rotating plug (RP), upper internal structure (UIS), intermediate heat exchanger (IHX), decay heat exchanger (DHX), primary pump, internal structure, internal components and reactor core. The IHXs transfer heat from the radioactive sodium coolant (primary sodium) in the primary heat transport system to the nonradioactive sodium coolant (secondary sodium) in the intermediate heat transport system. Each sodium flows like Fig. 1. Primary sodium flows inside of tube and secondary sodium flows outside. During transferring heat two sodium to sodium, the fluid-elastic instability is occurred among tube bundle by cross flow. Large amplitude vibration occurred by the fluid-elastic instability is caused such as crack and wear of tube. Thus it is important to decrease the fluid-elastic instability in terms of a safety. The purpose of this paper is to evaluate the fluid-elastic instability for tube bundle in the IHX following ASME code. This paper evaluated the fluid-elastic instability of tube bundle in the SFR IHX. According evaluation results, the fluid-elastic instability of IHX tube bundle is occurred. A installing an additional TSP under the upper tubesheet can decrease a probability of fluid-elastic instability. If a location of an additional TSP does not exceed tube length to become a 750 mm, tube bundle of IHX is safety from the fluid-elastic instability

  10. Neutron star pulsations and instabilities

    International Nuclear Information System (INIS)

    Lindblom, L.

    2001-01-01

    Gravitational radiation (GR) drives an instability in certain modes of rotating stars. This instability is strong enough in the case of the r-modes to cause their amplitudes to grow on a timescale of tens of seconds in rapidly rotating neutron stars. GR emitted by these modes removes angular momentum from the star at a rate which would spin it down to a relatively small angular velocity within about one year, if the dimensionless amplitude of the mode grows to order unity. A pedagogical level discussion is given here on the mechanism of GR instability in rotating stars, on the relevant properties of the r-modes, and on our present understanding of the dissipation mechanisms that tend to suppress this instability in neutron stars. The astrophysical implications of this GR driven instability are discussed for young neutron stars, and for older systems such as low mass x-ray binaries. Recent work on the non-linear evolution of the r-modes is also presented. (author)

  11. Geological structure of Osaka basin and characteristic distributions of structural damage caused by earthquake; Osaka bonchi kozo to shingai tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, K; Shiono, K; Inoue, N; Senda, S [Osaka City University, Osaka (JP. Faculty of Science); Ryoki, K [Osaka Polytechnic Collage, Osaka (Japan); Shichi, R [Nagoya University, Nagoya (Japan). Faculty of Science

    1996-05-01

    The paper investigates relations between the damage caused by the Hyogo-ken Nanbu earthquake and the deep underground structures. A characteristic of the earthquake damage distribution is that the damage concentrated near faults. Most of the damages were seen on the side of faults` relatively falling rather than right above the faults and of their slightly slanting to the seaside. Distribution like this seems to be closely related to underground structures. Therefore, a distribution map of the depth of basement granite in Osaka sedimentary basin was drawn, referring to the data on basement rock depth obtained from the distribution map of gravity anomaly and the result of the survey using the air gun reflection method. Moreover, cubic underground structures were determined by 3-D gravity analysis. The result was concluded as follows: when observing the M7 zone of the low land, in particular, where the damage was great from an aspect of gravity anomaly, the basement rock below the zone declined near the cliff toward the sea, which indicates a great possibility of its being a fault. There is a high possibility that the zone suffered mostly from the damage caused by focusing by refraction and total reflection of seismic wave rays. 3 refs., 8 figs.

  12. ALS-causing profilin-1-mutant forms a non-native helical structure in membrane environments.

    Science.gov (United States)

    Lim, Liangzhong; Kang, Jian; Song, Jianxing

    2017-11-01

    Despite having physiological functions completely different from superoxide dismutase 1 (SOD1), profilin 1 (PFN1) also carries mutations causing amyotrophic lateral sclerosis (ALS) with a striking similarity to that triggered by SOD1 mutants. Very recently, the C71G-PFN1 has been demonstrated to cause ALS by a gain of toxicity and the acceleration of motor neuron degeneration preceded the accumulation of its aggregates. Here by atomic-resolution NMR determination of conformations and dynamics of WT-PFN1 and C71G-PFN1 in aqueous buffers and in membrane mimetics DMPC/DHPC bicelle and DPC micelle, we deciphered that: 1) the thermodynamic destabilization by C71G transforms PFN1 into coexistence with the unfolded state, which is lacking of any stable tertiary/secondary structures as well as restricted ps-ns backbone motions, thus fundamentally indistinguishable from ALS-causing SOD1 mutants. 2) Most strikingly, while WT-PFN1 only weakly interacts with DMPC/DHPC bicelle without altering the native structure, C71G-PFN1 acquires abnormal capacity in strongly interacting with DMPC/DHPC bicelle and DPC micelle, energetically driven by transforming the highly disordered unfolded state into a non-native helical structure, similar to what has been previously observed on ALS-causing SOD1 mutants. Our results imply that one potential mechanism for C71G-PFN1 to initiate ALS might be the abnormal interaction with membranes as recently established for SOD1 mutants. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. [Instability of the distal radioulnar joint: Treatment options for ulnar lesions of the triangular fibrocartilage complex].

    Science.gov (United States)

    Spies, C K; Prommersberger, K J; Langer, M; Müller, L P; Hahn, P; Unglaub, F

    2015-08-01

    Injuries of the triangular fibrocartilage complex (TFCC) may be fatal to the distal radioulnar joint (DRUJ). This structure is one of the crucial stabilizers and guarantees unrestricted pronosupination of the forearm. A systematic examination is mandatory to diagnose DRUJ instability reliably. A clinical examination in comparison to the contralateral side is obligatory. Plain radiographs are required to exclude osseous lesions or deformities. Computed tomography of both wrists in neutral, pronation and supination is necessary to verify DRUJ instability in ambiguous situations. Based on a systematic examination wrist and DRUJ arthroscopy identify lesions clearly. Injuries of the radioulnar ligaments which entail DRUJ instability, should be reconstructed preferably anatomically. Ulnar-sided TFCC lesions may often cause DRUJ instability. Osseous ligament avulsions are mostly treated osteosynthetically. Ligament tears may be refixated using anchor or transosseous sutures. Tendon transplants are necessary for an anatomical reconstruction in cases of irreparable ruptures.

  14. Richtmyer–Meshkov instability of a thermal interface in a two-fluid plasma

    KAUST Repository

    Bond, D.

    2017-11-03

    We computationally investigate the Richtmyer–Meshkov instability of a density interface with a single-mode perturbation in a two-fluid, ion–electron plasma with no initial magnetic field. Self-generated magnetic fields arise subsequently. We study the case where the density jump across the initial interface is due to a thermal discontinuity, and select plasma parameters for which two-fluid plasma effects are expected to be significant in order to elucidate how they alter the instability. The instability is driven via a Riemann problem generated precursor electron shock that impacts the density interface ahead of the ion shock. The resultant charge separation and motion generates electromagnetic fields that cause the electron shock to degenerate and periodically accelerate the electron and ion interfaces, driving Rayleigh–Taylor instability. This generates small-scale structures and substantially increases interfacial growth over the hydrodynamic case.

  15. Turing Instability-Driven Biofabrication of Branching Tissue Structures: A Dynamic Simulation and Analysis Based on the Reaction–Diffusion Mechanism †

    Directory of Open Access Journals (Sweden)

    Xiaolu Zhu

    2018-03-01

    Full Text Available Four-dimensional (4D biofabrication techniques aim to dynamically produce and control three-dimensional (3D biological structures that would transform their shapes or functionalities with time, when a stimulus is imposed or cell post-printing self-assembly occurs. The evolution of 3D branching patterns via self-assembly of cells is critical for the 4D biofabrication of artificial organs or tissues with branched geometry. However, it is still unclear how the formation and evolution of these branching patterns are biologically encoded. Here, we study the biofabrication of lung branching structures utilizing a simulation model based on Turing instability that raises a dynamic reaction–diffusion (RD process of the biomolecules and cells. The simulation model incorporates partial differential equations of four variables, describing the tempo-spatial distribution of the variables in 3D over time. The simulation results present the formation and evolution process of 3D branching patterns over time and also interpret both the behaviors of side-branching and tip-splitting as the stalk grows and the fabrication style under an external concentration gradient of morphogen, through 3D visualization. This provides a theoretical framework for rationally guiding the 4D biofabrication of lung airway grafts via cellular self-organization, which would potentially reduce the complexity of future experimental research and number of trials.

  16. Bosonic instability of charged black holes

    International Nuclear Information System (INIS)

    Gaina, A.B.; Ternov, I.M.

    1986-01-01

    The processes of spontaneous and induced production and accumulation of charged bosons on quasibound superradiant levels in the field of Kerr-Newman black hole is analysed. It is shown that bosonic instability may be caused exclusively by the rotation of the black hole. Particulary, the Reissner-Nordstrom configuration is stable. In the case of rotating and charged black hole the bosonic instability may cause an increase of charge of the black hole

  17. Genetic instability associated with loop or stem–loop structures within transcription units can be independent of nucleotide excision repair

    Science.gov (United States)

    Burns, John A; Chowdhury, Moinuddin A; Cartularo, Laura; Berens, Christian; Scicchitano, David A

    2018-01-01

    Abstract Simple sequence repeats (SSRs) are found throughout the genome, and under some conditions can change in length over time. Germline and somatic expansions of trinucleotide repeats are associated with a series of severely disabling illnesses, including Huntington's disease. The underlying mechanisms that effect SSR expansions and contractions have been experimentally elusive, but models suggesting a role for DNA repair have been proposed, in particular the involvement of transcription-coupled nucleotide excision repair (TCNER) that removes transcription-blocking DNA damage from the transcribed strand of actively expressed genes. If the formation of secondary DNA structures that are associated with SSRs were to block RNA polymerase progression, TCNER could be activated, resulting in the removal of the aberrant structure and a concomitant change in the region's length. To test this, TCNER activity in primary human fibroblasts was assessed on defined DNA substrates containing extrahelical DNA loops that lack discernible internal base pairs or DNA stem–loops that contain base pairs within the stem. The results show that both structures impede transcription elongation, but there is no corresponding evidence that nucleotide excision repair (NER) or TCNER operates to remove them. PMID:29474673

  18. HIV reservoirs and immune surveillance evasion cause the failure of structured treatment interruptions: a computational study.

    Directory of Open Access Journals (Sweden)

    Emiliano Mancini

    Full Text Available Continuous antiretroviral therapy is currently the most effective way to treat HIV infection. Unstructured interruptions are quite common due to side effects and toxicity, among others, and cannot be prevented. Several attempts to structure these interruptions failed due to an increased morbidity compared to continuous treatment. The cause of this failure is poorly understood and often attributed to drug resistance. Here we show that structured treatment interruptions would fail regardless of the emergence of drug resistance. Our computational model of the HIV infection dynamics in lymphoid tissue inside lymph nodes, demonstrates that HIV reservoirs and evasion from immune surveillance themselves are sufficient to cause the failure of structured interruptions. We validate our model with data from a clinical trial and show that it is possible to optimize the schedule of interruptions to perform as well as the continuous treatment in the absence of drug resistance. Our methodology enables studying the problem of treatment optimization without having impact on human beings. We anticipate that it is feasible to steer new clinical trials using computational models.

  19. Alternative approaches used to assess structural changes of natural zircon caused by heat treatment

    Science.gov (United States)

    Huong, L. T. T.; Thuyet, N. T. M.; Phan, T. L.; Tran, N.; Toan, D. N.; Thang, P. D.; Huy, B. T.

    2018-03-01

    It is known that large changes in the crystal structure of zircon (ZrSiO4) can be assessed through the linewidth of the characteristic Raman mode (Δν3) at 1008 cm-1. However, the use of Δν3 to assess small changes caused by heat treatment at temperatures below its decomposition temperature of 1670 °C is difficult. The present work points out that the combination of X-ray diffraction (XRD) analyses, and photoluminescence (PL) and Raman (RS) measurements with different excitation wavelengths is an effective approach to solve the above problem. In this context, we have selected natural zircon containing some rare-earth (RE) impurities, and then studied the changes in its crystal structure caused by heat treatment at temperatures Tan=400-1600 °C. XRD analyses reveal that small modifications of the unit-cell parameters occur as Tan>600 °C. Taking the intensity ratios of the ν3 mode to RE-related emissions (Iν3/IRE) or the PL intensity ratios between RE-related emissions into consideration, the similar results in good agreement with the XRD analyses are also found. We believe that the small structural changes are related to the migration and redistribution of defects and impurities, and re-crystallization of zircon. This could be further confirmed though the relation between paramagnetic and ferromagnetic signals when Tan changes.

  20. Performance through Deformation and Instability

    Science.gov (United States)

    Bertoldi, Katia

    2015-03-01

    Materials capable of undergoing large deformations like elastomers and gels are ubiquitous in daily life and nature. An exciting field of engineering is emerging that uses these compliant materials to design active devices, such as actuators, adaptive optical systems and self-regulating fluidics. Compliant structures may significantly change their architecture in response to diverse stimuli. When excessive deformation is applied, they may eventually become unstable. Traditionally, mechanical instabilities have been viewed as an inconvenience, with research focusing on how to avoid them. Here, I will demonstrate that these instabilities can be exploited to design materials with novel, switchable functionalities. The abrupt changes introduced into the architecture of soft materials by instabilities will be used to change their shape in a sudden, but controlled manner. Possible and exciting applications include materials with unusual properties such negative Poisson's ratio, phononic crystals with tunable low-frequency acoustic band gaps and reversible encapsulation systems.

  1. Dynamic response of the high flux isotope reactor structure caused by nearby heavy load drop

    International Nuclear Information System (INIS)

    Chang, Shih-Jung.

    1995-01-01

    A heavy load of 50,000 lb is assumed to drop from 10 ft above the bottom of the High Flux Isotope Reactor (HFIR) pool at the loading station. The consequences of the dynamic impact to the bottom slab of the pool and to the nearby HFIR reactor vessel are analyzed by applying the ABAQUS computer code The results show that both the BM vessel structure and its supporting legs are subjected to elastic disturbances only and, therefore, will not be damaged. The bottom slab of the pool, however, will be damaged to about half of the slab thickness. The velocity response spectrum at the concrete floor next to the HFIR vessel as a result of the vibration caused by the impact is obtained. It is concluded, that the damage caused by heavy load drop at the loading station is controlled by the slab damage and the nearby HFIR vessel and the supporting legs will not be damaged

  2. Investigations of the changes in the bentonite structure caused by the different treatments

    Directory of Open Access Journals (Sweden)

    Stojiljković S.

    2015-01-01

    Full Text Available The bentonite was treated in different ways and the changes in structure were monitored. Acid activation with sulphuric acid of investigated bentonite caused the increase in specific volume of micropore-mesopore. It was shown that activation by acid obtained at a constant temperature and constant period of time provides the possibility to obtain samples of bentonite of searched porosity only by changing the concentration of sulphuric and hydrochloric acid. By thermal activation of bentonite clay in the temperature range 100-1100 0C, samples of desired porosity were acquired. [Projekat Ministarstva nauke Republike Srbije, br. 174007i br. TR 34020

  3. Manual on the Fatigue of Structures. II. Causes and Prevention of Damage. 7. Mechanical Surface Damage,

    Science.gov (United States)

    1981-06-01

    AO-A103 «29 ADVISORY 6R0UP FOR AEROSPACE RESEARCH AND DEVELOPMENT—ETC F/O 20/11 MANUAL ON THE FATIfUE OF STRUCTURES. IX. CAUSES AND PREVENTION —ETC... stresses . In the case of 99.999% pure aluminium Vyas and Preece240 investigated the changes in the surface finish of the metal under the electron...during the erosion process. In the case of annealed nickel and of electrolytically polished test specimens cavitation- stressed in distilled water at 25°C

  4. Ventricular dyssynchrony as a cause of structural disease in the heart of Dorper sheep

    Directory of Open Access Journals (Sweden)

    J. Ker

    2004-11-01

    Full Text Available Ventricular dyssynchrony is a disturbance of the normal, organized electromechanical coupling of the two ventricles. This condition has many causes, such as left bundle branch block, ventricular preexcitation, right ventricular pacing and right ventricular premature ventricular complexes (PVCs. Ventricular dyssynchrony has many adverse haemodynamic effects on the left ventricle and we wanted to know whether these adverse haemodynamic effects might have any structural consequences on the left ventricles of such hearts. Six healthy Dorper wethers were subjected to numerous right ventricular PVCs to induce ventricular dyssynchrony in order to determine whether any structural consequences will occur in the left ventricles of these hearts. Myocarditis in the musculature of the left ventricles of all six these hearts was seen.

  5. Unique Optoelectronic Structure and Photoreduction Properties of Sulfur-Doped Lead Chromates Explaining Their Instability in Paintings.

    Science.gov (United States)

    Rahemi, Vanoushe; Sarmadian, Nasrin; Anaf, Willemien; Janssens, Koen; Lamoen, Dirk; Partoens, Bart; De Wael, Karolien

    2017-03-21

    Chrome yellow refers to a group of synthetic inorganic pigments that became popular as an artist's material from the second quarter of the 19th century. The color of the pigment, in which the chromate ion acts as a chromophore, is related to its chemical composition (PbCr 1-x S x O 4 , with 0 ≤ x ≤ 0.8) and crystalline structure (monoclinic/orthorhombic). Their shades range from the yellow-orange to the paler yellow tones with increasing sulfate amount. These pigments show remarkable signs of degradation after limited time periods. Pure PbCrO 4 (crocoite in its natural form) has a deep yellow color and is relatively stable, while the coprecipitate with lead sulfate (PbCr 1-x S x O 4 ) has a paler shade and seems to degrade faster. This degradation is assumed to be related to the reduction of Cr(VI) to Cr(III). We show that, when the the sulfur(S)-content in chrome yellow increases, the band gap increases. Typically, when increasing the band gap, one might assume that a decrease in photoactivity is the result. However, the photoactivity relative to the Cr content and, thus, Cr reduction of sulfur-rich PbCr 1-x S x O 4 is found to be much higher compared to the sulfur-poor or nondoped lead chromates. This discrepancy can be explained by the evolution of the crystal and electronic structure as a function of the sulfur content: first-principles density functional theory calculations show that both the absorption coefficient and reflection coefficients of the lead chromates change as a result of the sulfate doping in such a way that the generation of electron-hole pairs under illumination relative to the total Cr content increases. These changes in the material properties explain why paler shade yellow colors of this pigment are more prone to discoloration. The electronic structure calculations also demonstrate that lead chromate and its coprecipitates are p-type semiconductors, which explains the observed reduction reaction. Because understanding this phenomenon is

  6. 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.

  7. Presentation of common cause failures in fault tree structure of Krsko PSA : an historical overview

    International Nuclear Information System (INIS)

    Vrbanic, I.; Kosutic, I.; Vukovic, I.; Simic, Z.

    2003-01-01

    Failure of multiple components due to a common cause represents one of the most important issues in evaluation of system reliability or unavailability. The frequency of such events has relatively low expectancy, when compared to random failures, which affect individual components. However, in many cases the consequence is a direct loss of safety system or mitigative safety function. For this reason, the modeling of a common cause failure (CCF) and its presentation in fault tree structure is of the uttermost importance in probabilistic safety analyses (PSA). During the past decade, PSA model of Krsko NPP has undergone many small changes and a couple of major ones in fulfilling its basic purpose, which was serving as a tool for providing an appropriate information on the risk associated with actual plant design and operation. All changes to Krsko PSA model were undertaken in order to make it a better tool and / or to make it represent the plant in more accurate manner. The paper provides an overview of changes in CCF modeling in the fault tree structure from the initial PSA model development till present. (author)

  8. EYS Mutations Causing Autosomal Recessive Retinitis Pigmentosa: Changes of Retinal Structure and Function with Disease Progression

    Directory of Open Access Journals (Sweden)

    David B. McGuigan

    2017-07-01

    Full Text Available Mutations in the EYS (eyes shut homolog gene are a common cause of autosomal recessive (ar retinitis pigmentosa (RP. Without a mammalian model of human EYS disease, there is limited understanding of details of disease expression and rates of progression of the retinal degeneration. We studied clinically and with chromatic static perimetry, spectral-domain optical coherence tomography (OCT, and en face autofluoresence imaging, a cohort of 15 patients (ages 12–51 at first visit, some of whom had longitudinal data of function and structure. Rod sensitivity was able to be measured by chromatic perimetry in most patients at their earliest visits and some patients retained patchy rod function into the fifth decade of life. As expected from RP, cone sensitivity persisted after rod function was no longer measurable. The photoreceptor nuclear layer of the central retina was abnormal except at the fovea in most patients at first visit. Perifoveal disease measured over a period of years indicated that photoreceptor structural loss was followed by dysmorphology of the inner retina and loss of retinal pigment epithelial integrity. Although there could be variability in severity, preliminary analyses of the rates of vision loss suggested that EYS is a more rapidly progressive disease than other ciliopathies causing arRP, such as USH2A and MAK.

  9. Structure and Dynamics of RNA Repeat Expansions That Cause Huntington's Disease and Myotonic Dystrophy Type 1.

    Science.gov (United States)

    Chen, Jonathan L; VanEtten, Damian M; Fountain, Matthew A; Yildirim, Ilyas; Disney, Matthew D

    2017-07-11

    RNA repeat expansions cause a host of incurable, genetically defined diseases. The most common class of RNA repeats consists of trinucleotide repeats. These long, repeating transcripts fold into hairpins containing 1 × 1 internal loops that can mediate disease via a variety of mechanism(s) in which RNA is the central player. Two of these disorders are Huntington's disease and myotonic dystrophy type 1, which are caused by r(CAG) and r(CUG) repeats, respectively. We report the structures of two RNA constructs containing three copies of a r(CAG) [r(3×CAG)] or r(CUG) [r(3×CUG)] motif that were modeled with nuclear magnetic resonance spectroscopy and simulated annealing with restrained molecular dynamics. The 1 × 1 internal loops of r(3×CAG) are stabilized by one-hydrogen bond (cis Watson-Crick/Watson-Crick) AA pairs, while those of r(3×CUG) prefer one- or two-hydrogen bond (cis Watson-Crick/Watson-Crick) UU pairs. Assigned chemical shifts for the residues depended on the identity of neighbors or next nearest neighbors. Additional insights into the dynamics of these RNA constructs were gained by molecular dynamics simulations and a discrete path sampling method. Results indicate that the global structures of the RNA are A-form and that the loop regions are dynamic. The results will be useful for understanding the dynamic trajectory of these RNA repeats but also may aid in the development of therapeutics.

  10. 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.

  11. Corona-induced electrohydrodynamic instabilities in low conducting liquids

    Energy Technology Data Exchange (ETDEWEB)

    Vega, F.; Perez, A.T. [Depto. Electronica y Electromagnetismo, Facultad de Fisica, Universidad de Sevilla, Avda. Reina Mercedes, s/n. 41012, Sevilla (Spain)

    2003-06-01

    The rose-window electrohydrodynamic (EHD) instability has been observed when a perpendicular field with an additional unipolar ion injection is applied onto a low conducting liquid surface. This instability has a characteristic pattern with cells five to 10 times greater than those observed in volume instabilities caused by unipolar injection. We have used corona discharge from a metallic point to perform some measurements of the rose-window instability in low conducting liquids. The results are compared to the linear theoretical criterion for an ohmic liquid. They confirmed that the minimum voltage for this instability is much lower than that for the interfacial instability in high conducting liquids. This was predicted theoretically in the dependence of the critical voltage as a function of the non-dimensional conductivity. It is shown that in a non-ohmic liquid the rose window appears as a secondary instability after the volume instability. (orig.)

  12. Instabilities in electromagnetic quasilevitation.

    Science.gov (United States)

    Spragg, Kirk; Letout, Sebastien; Ernst, R; Sneyd, Alfred; Fautrelle, Yves

    2014-05-01

    We investigate free-surface instabilities occurring in various industrial processes involving liquid metal. Of particular interest is the behavior of the free surface of a pool of liquid metal when it is submitted to an alternating magnetic field. Experimentally, we study the effect of a vertical alternating medium-frequency magnetic field on an initially circular pool. We observe various types of behavior according to magnetic field amplitude, e.g., axisymmetric deformations, azimuthal mode structures, slow radial oscillation of the pool perimeter, and random rotation of the pool around its center. Drop rotation could be attributed to nonsymmetric shape deformations. The effect of oxidation leads to drastic changes in pool behavior. The experimental results are then compared to a linear stability analysis of the free surface of a circular liquid drop.

  13. The cause of spatial structure in solar He I 1083 nm multiplet images

    Science.gov (United States)

    Leenaarts, Jorrit; Golding, Thomas; Carlsson, Mats; Libbrecht, Tine; Joshi, Jayant

    2016-10-01

    Context. The He I 1083 nm is a powerful diagnostic for inferring properties of the upper solar chromosphere, in particular for the magnetic field. The basic formation of the line in one-dimensional models is well understood, but the influence of the complex three-dimensional structure of the chromosphere and corona has however never been investigated. This structure must play an essential role because images taken in He I 1083 nm show structures with widths down to 100 km. Aims: We aim to understand the effect of the three-dimensional temperature and density structure in the solar atmosphere on the formation of the He I 1083 nm line. Methods: We solved the non-LTE radiative transfer problem assuming statistical equilibrium for a simple nine-level helium atom that nevertheless captures all essential physics. As a model atmosphere we used a snapshot from a 3D radiation-MHD simulation computed with the Bifrost code. Ionising radiation from the corona was self-consistently taken into account. Results: The emergent intensity in the He I 1083 nm is set by the source function and the opacity in the upper chromosphere. The former is dominated by scattering of photospheric radiation and does not vary much with spatial location. The latter is determined by the photonionisation rate in the He I ground state continuum, as well as the electron density in the chromosphere. The spatial variation of the flux of ionising radiation is caused by the spatially-structured emissivity of the ionising photons from material at T ≈ 100 kK in the transition region. The hotter coronal material produces more ionising photons, but the resulting radiation field is smooth and does not lead to small-scale variation of the UV flux. The corrugation of the transition region further increases the spatial variation of the amount of UV radiation in the chromosphere. Finally we find that variations in the chromospheric electron density also cause strong variation in He I 1083 nm opacity. We compare our

  14. Structural and functional alterations of catalase induced by acriflavine, a compound causing apoptosis and necrosis.

    Science.gov (United States)

    Attar, Farnoosh; Khavari-Nejad, Sarah; Keyhani, Jacqueline; Keyhani, Ezzatollah

    2009-08-01

    Acriflavine is an antiseptic agent causing both apoptosis and necrosis in yeast. In this work, its effect on the structure and function of catalase, a vital enzyme actively involved in protection against oxidative stress, was investigated. In vitro kinetic studies showed that acriflavine inhibited the enzymatic activity in a competitive manner. The residual activity detectable after preincubation of catalase (1.5 nmol/L) with various concentrations of acriflavine went from 50% to 20% of the control value as the acriflavine concentration increased from 30 to 90 micromol/L. Correlatively with the decrease in activity, alterations in the enzyme's conformation were observed as indicated by fluorescence spectroscopy, circular dichroism spectroscopy, and electronic absorption spectroscopy. The enzyme's intrinsic fluorescence obtained upon excitation at either 297 nm (tryptophan residues) or 280 nm (tyrosine and tryptophan residues) decreased as a function of acriflavine concentration. Circular dichroism studies showed alterations of the protein structure by acriflavine with up to 13% decrease in alpha helix, 16% increase in beta-sheet content, 17% increase in random coil, and 4% increase in beta turns. Spectrophotometric studies showed a blueshift and modifications in the chromicity of catalase at 405 nm, corresponding to an absorbance band due to the enzyme's prosthetic group. Thus, acriflavine induced in vitro a profound change in the structure of catalase so that the enzyme could no longer function. Our results showed that acriflavine, a compound producing apoptosis and necrosis, can have a direct effect on vital functions in cells by disabling key enzymes.

  15. Transverse Resonant Vibration of Non-Bearing Structures Caused by Wind

    Science.gov (United States)

    Jendzelovsky, Norbert; Antal, Roland

    2017-10-01

    Nowadays, there are increasing use of very thin, subtle and light structures in the field of building constructions. We can find such a structures as part of roofs or design facades. By using these lamellas like, non-bearing structures as a part of architectural design of buildings, it is necessary to consider wind effects on these structures. Subtle structures of this type are prone to vibration in the transverse direction of the wind flow. The fact that the vibration occurs depends on wind parameters (wind velocity, direction of an air flow) and it also depends on the properties of lamella (shape, length, mass, natural frequency, support type). The principal idea of this article is to show susceptibility of lamellae-like structures to transverse resonant vibration caused by the phenomenon called Von Karman effect. Comparison of susceptibility to transverse resonance vibration was analysed on the different shapes of lamellas loaded by different wind speed. Analysis was based on usage of empirically derived equations. Von Karman effect arise from wind flow past an object. Turbulence in the form of vortices are formed at the object and shed into the flowing stream intermittently. The potential problem is that this turbulence can induce vibrations into the lamella itself. In terms of this vibration problem, two frequencies are interesting. Von Karman shedding frequency is the frequency at which the vortices are formed and shed at the object. The vortex-shedding frequency increases with the velocity of the wind flow and decreases with the size of the object. Natural frequency of the object depends on the construction of the lamella itself. Parameters of lamella as a shape, mass, length, elasticity modulus of material and support types are directly involved in the calculation of natural frequency. Worst case scenario in the term of transverse resonant vibration occurs when the natural frequency of lamella is equal to the vortex-shedding frequency. In this case

  16. Treatment of the subject of tearing instability

    International Nuclear Information System (INIS)

    Paris, P.C.

    1977-07-01

    A simple approach is taken to the mechanics of potential instability associated with the steady tearing portion of J-Integral R-curves. The analysis is developed from simple examples of structural component (or test specimen) configurations with cracks, examining their instability possibilities individually, in order to draw more general conclusions about elastic-plastic cracking instability as contrasted to linear-elastic behavior. Finally, an attempt is made to model a more local cleavage-like instability for material in the fracture process zone just ahead of a crack tip. Results are then presented of a testing program which clearly demonstrates the appropriateness of the tearing instability analysis and which illustrates its broad potential for future application, as well as presenting guidelines for its further development. The material selected for analysis was Ni-Cr-Mo-V rotor steel

  17. Taylor instability in rhyolite lava flows

    Science.gov (United States)

    Baum, B. A.; Krantz, W. B.; Fink, J. H.; Dickinson, R. E.

    1989-01-01

    A refined Taylor instability model is developed to describe the surface morphology of rhyolite lava flows. The effect of the downslope flow of the lava on the structures resulting from the Taylor instability mechanism is considered. Squire's (1933) transformation is developed for this flow in order to extend the results to three-dimensional modes. This permits assessing why ridges thought to arise from the Taylor instability mechanism are preferentially oriented transverse to the direction of lava flow. Measured diapir and ridge spacings for the Little and Big Glass Mountain rhyolite flows in northern California are used in conjunction with the model in order to explore the implications of the Taylor instability for flow emplacement. The model suggests additional lava flow features that can be measured in order to test whether the Taylor instability mechanism has influenced the flows surface morphology.

  18. Mechanical reliability of porous low-k dielectrics for advanced interconnect: Study of the instability mechanisms in porous low-k dielectrics and their mediation through inert plasma induced re-polymerization of the backbone structure

    Science.gov (United States)

    Sa, Yoonki

    Continuous scaling down of critical dimensions in interconnect structures requires the use of ultralow dielectric constant (k) films as interlayer dielectrics to reduce resistance-capacitance delays. Porous carbon-doped silicon oxide (p-SiCOH) dielectrics have been the leading approach to produce these ultralow-k materials. However, embedding of porosity into dielectric layer necessarily decreases the mechanical reliability and increases its susceptibility to adsorption of potentially deleterious chemical species during device fabrication process. Among those, exposure of porous-SiCOH low-k (PLK) dielectrics to oxidizing plasma environment causes the increase in dielectric constant and their vulnerability to mechanical instability of PLKs due to the loss of methyl species and increase in moisture uptake. These changes in PLK properties and physical stability have been persisting challenges for next-generation interconnects because they are the sources of failure in interconnect integration as well as functional and physical failures appearing later in IC device manufacturing. It is therefore essential to study the fundamentals of the interactions on p-SiCOH matrix induced by plasma exposure and find an effective and easy-to-implement way to reverse such changes by repairing damage in PLK structure. From these perspectives, the present dissertation proposes 1) a fundamental understanding of structural transformation occurring during oxidative plasma exposure in PLK matrix structure and 2) its restoration by using silylating treatment, soft x-ray and inert Ar-plasma radiation, respectively. Equally important, 3) as an alternative way of increasing the thermo-mechanical reliability, PLK dielectric film with an intrinsically robust structure by controlling pore morphology is fabricated and investigated. Based on the investigations, stability of PLK films studied by time-dependent ball indentation tester under the elevated temperature, variation in film thickness and

  19. New instability strip for hot degenerates

    International Nuclear Information System (INIS)

    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 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

  20. Changes in brown coal structure caused by coal-solubilizing microorganisms

    Energy Technology Data Exchange (ETDEWEB)

    Schmiers, H.; Koepsel, R.; Weber, A.; Winkelhoefer, M.; Grosse, S. [Technische Univ. Bergakademie Freiberg (Germany). Inst. fuer Energieverfahrenstechnik und Chemieingenieurwesen

    1997-12-31

    The phenomenon of coal solubilization caused by microorganisms has been explained by various mechanisms: extraction of non-covalently bonded polar components of the coal substance by biogenic agents (chelating agents, alkaline substances) and enzyme-catalyzed cleavage of covalent bonds by extracellular enzyme systems. For this it is assumed that bond cleavage occurs on the aliphatic carbon (methylene groups, aliphatic bridges or on ester groups). As the coal has usually been treated with oxidizing agents such as H{sub 2}O{sub 2} or HNO{sub 3} before bioconversion, there is a possibility that the result of bioconversion is overlaid with the effect of the chemical treatment. We therefore studied the structural changes in the organic coal substance during pre-oxidation with H{sub 2}O{sub 2}, treatment with MnP and conversion using the fungal strains of Trichoderma and Fusarium oxysporum. (orig.)

  1. Cultural diversity, economic development and societal instability

    Science.gov (United States)

    Nettle, D.; Grace, J.B.; Choisy, M.; Cornell, H.V.; Guegan, J.-F.; Hochberg, M.E.

    2007-01-01

    Background. 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 on ?? diversity, but also diversity between a nation and its neighbours or ?? 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. Methodology/Principal Findings. We assembled a large cross-national dataset with information on ?? and ?? 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 type and domains of diversity have interacting effects. As previously documented, linguistic ?? 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 ?? diversity, the higher the linguistic diversity among nations in a region, the less stable the nation. But, religious ?? diversity has the opposite effect, reducing instability, particularly in the presence of high linguistic diversity. Conclusions. 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.

  2. Electron beam instabilities in gyrotron beam tunnels

    International Nuclear Information System (INIS)

    Pedrozzi, M.; Alberti, S.; Hogge, J.P.; Tran, M.Q.; Tran, T.M.

    1997-10-01

    Electron beam instabilities occurring in a gyrotron electron beam can induce an energy spread which might significantly deteriorate the gyrotron efficiency. Three types of instabilities are considered to explain the important discrepancy found between the theoretical and experimental efficiency in the case of quasi-optical gyrotrons (QOG): the electron cyclotron maser instability, the Bernstein instability and the Langmuir instability. The low magnetic field gradient in drift tubes of QOG makes that the electron cyclotron maser instability can develop in the drift tube at very low electron beam currents. Experimental measurements show that with a proper choice of absorbing structures in the beam tunnel, this instability can be suppressed. At high beam currents, the electrostatic Bernstein instability can induce a significant energy spread at the entrance of the interaction region. The induced energy spread scales approximately linearly with the electron beam density and for QOG one observes that the beam density is significantly higher than the beam density of an equivalent cylindrical cavity gyrotron. (author) figs., tabs., refs

  3. 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.

  4. Organotin compounds cause structure-dependent induction of progesterone in human choriocarcinoma Jar cells.

    Science.gov (United States)

    Hiromori, Youhei; Yui, Hiroki; Nishikawa, Jun-ichi; Nagase, Hisamitsu; Nakanishi, Tsuyoshi

    2016-01-01

    Organotin compounds, such as tributyltin (TBT) and triphenyltin (TPT), are typical environmental contaminants and suspected endocrine-disrupting chemicals because they cause masculinization in female mollusks. In addition, previous studies have suggested that the endocrine disruption by organotin compounds leads to activation of peroxisome proliferator-activated receptor (PPAR)γ and retinoid X receptor (RXR). However, whether organotin compounds cause crucial toxicities in human development and reproduction is unclear. We here investigated the structure-dependent effect of 12 tin compounds on mRNA transcription of 3β-hydroxysteroid dehydrogenase type I (3β-HSD I) and progesterone production in human choriocarcinoma Jar cells. TBT, TPT, dibutyltin, monophenyltin, tripropyltin, and tricyclohexyltin enhanced progesterone production in a dose-dependent fashion. Although tetraalkyltin compounds such as tetrabutyltin increased progesterone production, the concentrations necessary for activation were 30-100 times greater than those for trialkyltins. All tested active organotins increased 3β-HSD I mRNA transcription. We further investigated the correlation between the agonistic activity of organotin compounds on PPARγ and their ability to promote progesterone production. Except for DBTCl2, the active organotins significantly induced the transactivation function of PPARγ. In addition, PPARγ knockdown significantly suppressed the induction of mRNA transcription of 3β-HSD I by all active organotins except DBTCl2. These results suggest that some organotin compounds promote progesterone biosynthesis in vitro by inducing 3β-HSD I mRNA transcription via the PPARγ signaling pathway. The placenta represents a potential target organ for these compounds, whose endocrine-disrupting effects might cause local changes in progesterone concentration in pregnant women. Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Understanding Etna flank instability through numerical models

    Science.gov (United States)

    Apuani, Tiziana; Corazzato, Claudia; Merri, Andrea; Tibaldi, Alessandro

    2013-02-01

    As many active volcanoes, Mount Etna shows clear evidence of flank instability, and different mechanisms were suggested to explain this flank dynamics, based on the recorded deformation pattern and character. Shallow and deep deformations, mainly associated with both eruptive and seismic events, are concentrated along recognised fracture and fault systems, mobilising the eastern and south-eastern flank of the volcano. Several interacting causes were postulated to control the phenomenon, including gravity force, magma ascent along the feeding system, and a very complex local and/or regional tectonic activity. Nevertheless, the complexity of such dynamics is still an open subject of research and being the volcano flanks heavily urbanised, the comprehension of the gravitative dynamics is a major issue for public safety and civil protection. The present research explores the effects of the main geological features (in particular the role of the subetnean clays, interposed between the Apennine-Maghrebian flysch and the volcanic products) and the role of weakness zones, identified by fracture and fault systems, on the slope instability process. The effects of magma intrusions are also investigated. The problem is addressed by integrating field data, laboratory tests and numerical modelling. A bi- and tri-dimensional stress-strain analysis was performed by a finite difference numerical code (FLAC and FLAC3D), mainly aimed at evaluating the relationship among geological features, volcano-tectonic structures and magmatic activity in controlling the deformation processes. The analyses are well supported by dedicated structural-mechanical field surveys, which allowed to estimate the rock mass strength and deformability parameters. To take into account the uncertainties which inevitably occur in a so complicated model, many efforts were done in performing a sensitivity analysis along a WNW-ESE section crossing the volcano summit and the Valle del Bove depression. This was

  6. Ground waves caused by gas cloud explosions and their effects on nuclear power plant structures

    International Nuclear Information System (INIS)

    Werkle, H.; Waas, G.

    1983-01-01

    The response of embedded structures to ground waves caused by the explosion of a gas cloud is studied. In the first step, the free field ground motion is analyzed; then the response of a PWR-building is computed. The analysis of the free-field motion is performed using a two-dimensional plane strain model, whereas the interaction problem of the structure excited by the free-field motion is investigated using an axisymmetric three-dimensional model. The soil is assumed to be viscoelastic and horizontally layered. The equations of motion for the viscoelastic continuum are solved in the frequency domain by a semianalytic method. The travelling surface loads from air pressure waves are represented by superposition of line loads. The superposition takes advantage of the mathematical properties of the Fourier transforms. Explicit ring load solutions are used to solve the three-dimensional interaction problem of a rigid embedded circular foundation excited by a two-dimensional wave field of Rayleigh wave type. (orig./WL)

  7. Ultra-structural defects cause low bone matrix stiffness despite high mineralization in osteogenesis imperfecta mice.

    Science.gov (United States)

    Vanleene, Maximilien; Porter, Alexandra; Guillot, Pascale-Valerie; Boyde, Alan; Oyen, Michelle; Shefelbine, Sandra

    2012-06-01

    Bone is a complex material with a hierarchical multi-scale organization from the molecule to the organ scale. The genetic bone disease, osteogenesis imperfecta, is primarily caused by mutations in the collagen type I genes, resulting in bone fragility. Because the basis of the disease is molecular with ramifications at the whole bone level, it provides a platform for investigating the relationship between structure, composition, and mechanics throughout the hierarchy. Prior studies have individually shown that OI leads to: 1. increased bone mineralization, 2. decreased elastic modulus, and 3. smaller apatite crystal size. However, these have not been studied together and the mechanism for how mineral structure influences tissue mechanics has not been identified. This lack of understanding inhibits the development of more accurate models and therapies. To address this research gap, we used a mouse model of the disease (oim) to measure these outcomes together in order to propose an underlying mechanism for the changes in properties. Our main finding was that despite increased mineralization, oim bones have lower stiffness that may result from the poorly organized mineral matrix with significantly smaller, highly packed and disoriented apatite crystals. Using a composite framework, we interpret the lower oim bone matrix elasticity observed as the result of a change in the aspect ratio of apatite crystals and a disruption of the crystal connectivity. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. Local damage to Ultra High Performance Concrete structures caused by an impact of aircraft engine missiles

    International Nuclear Information System (INIS)

    Riedel, Werner; Noeldgen, Markus; Strassburger, Elmar; Thoma, Klaus; Fehling, Ekkehard

    2010-01-01

    Research highlights: → Experimental series on UHPC panels subjected to aircraft engine impact. → Improved ballistic limit of fiber reinforced UHPC in comparison to conventional R/C. → Detailed investigation of failure mechanisms of fiber reinforced UHPC panel. - Abstract: The impact of an aircraft engine missile causes high stresses, deformations and a severe local damage to conventional reinforced concrete. As a consequence the design of R/C protective structural elements results in components with rather large dimensions. Fiber reinforced Ultra High Performance Concrete (UHPC) is a concrete based material which combines ultra high strength, high packing density and an improved ductility with a significantly increased energy dissipation capacity due to the addition of fiber reinforcement. With those attributes the material is potentially suitable for improved protective structural elements with a reduced need for material resources. The presented paper reports on an experimental series of scaled aircraft engine impact tests with reinforced UHPC panels. The investigations are focused on the material behavior and the damage intensity in comparison to conventional concrete. The fundamental work of is taken as reference for the evaluation of the results. The impactor model of a Phantom F4 GE-J79 engine developed and validated by Sugano et al. is used as defined in the original work. In order to achieve best comparability, the experimental configuration and method are adapted for the UHPC experiments. With 'penetration', 'scabbing' and 'perforation' all relevant damage modes defined in are investigated so that a full set of results are provided for a representative UHPC structural configuration.

  9. Generalized laser filamentation instability coupled to cooling instability

    International Nuclear Information System (INIS)

    Liang, E.P.; Wong, J.; Garrison, J.

    1984-01-01

    We consider the propagation of laser light in an initially slightly nonuniform plasma. The classical dispersion relation for the laser filamentation growth rate (see e.g., B. Langdon, in the 1980 Lawrence Livermore National Laboratory Laser Program Annual Report, pp. 3-56, UCRL-50021-80, 1981) can be generalized to include other acoustical effects. For example, we find that the inclusion of potential imbalances in the heating and cooling rates of the ambient medium due to density and temperature perturbations can cause the laser filamentation mode to bifurcate into a cooling instability mode at long acoustic wavelengths. We also attempt to study semi-analytically the nonlinear evolution of this and related instabilities. These results have wide applications to a variety of chemical gas lasers and phenomena related to laser-target interactions (e.g., jet-like behavior)

  10. Chromosomal instability determines taxane response

    DEFF Research Database (Denmark)

    Swanton, C.; Nicke, B.; Schuett, M.

    2009-01-01

    chromosomal instability (CIN). Silencing 22/50 of these genes, many of which are involved in DNA repair, caused cancer cell death, suggesting that these genes are involved in the survival of aneuploid cells. Overexpression of these "CIN-survival'' genes is associated with poor outcome in estrogen receptor......-positive breast cancer and occurs frequently in basal-like and Her2-positive cases. In diploid cells, but not in chromosomally unstable cells, paclitaxel causes repression of CIN-survival genes, followed by cell death. In the OV01 ovarian cancer clinical trial, a high level of CIN was associated with taxane...

  11. End Point of Black Ring Instabilities and the Weak Cosmic Censorship Conjecture.

    Science.gov (United States)

    Figueras, Pau; Kunesch, Markus; Tunyasuvunakool, Saran

    2016-02-19

    We produce the first concrete evidence that violation of the weak cosmic censorship conjecture can occur in asymptotically flat spaces of five dimensions by numerically evolving perturbed black rings. For certain thin rings, we identify a new, elastic-type instability dominating the evolution, causing the system to settle to a spherical black hole. However, for sufficiently thin rings the Gregory-Laflamme mode is dominant, and the instability unfolds similarly to that of black strings, where the horizon develops a structure of bulges connected by necks which become ever thinner over time.

  12. Hydrodynamic instabilities in inertial fusion

    International Nuclear Information System (INIS)

    Hoffman, N.M.

    1994-01-01

    This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interactions in intermediate-stage Rayleigh-Taylor instability

  13. Between information systems and physical structure of the city: New causes of climate changes

    Directory of Open Access Journals (Sweden)

    Mihajlov Vladimir

    2011-01-01

    Full Text Available Because of the frequent and significant spatial transformations, an increasing climate change regime in urban areas occurs. In this paper a comprehensive reflection on these changes is analyzed, concerning one of the major causes - the social transformation and the growing use of information, networks and technology, used by city dwellers in everyday life. Advanced communications and the Internet provide urban concentration and decentralization, creating new spatial and geographic network, with a new allocation of space, for manufacturing and services. The consequence may be recognized in increasing individualization and social habits of city dwellers, as well as in modified way of households use, changing neighbourhoods and public spaces, transport systems, as the final outcome is the climate change. In this paper, the interdependence between information networks is emphasized - between virtual and physical environment, as well as changes in the way of life of the city, which ultimately lead to a new trigger for climate change. Users have never been more mobile in the physical space (commuting and tourist travel, while in the virtual space they are associated with the fixed points - everybody can be located, by using email or social network. Unexpectedly, the cause of the problem which is considered in this paper, is increased mobility in the real space, while city dwellers remain in one place, by using their virtual electronic connections. Thus, the role of city dwellers in creating climate change depends upon their spatial distribution and relationship towards information's and network activity. As a result, the drivers in city development are recognized on network nodes. Current crises in the global environment (economic, climate and social indicate the need to develop multi-functional environment and a greater appreciation of natural factors. Therefore, as a decisive factor for the adaptation of urban structure on climate change is the

  14. 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...

  15. Genomic structural variation-mediated allelic suppression causes hybrid male sterility in rice.

    Science.gov (United States)

    Shen, Rongxin; Wang, Lan; Liu, Xupeng; Wu, Jiang; Jin, Weiwei; Zhao, Xiucai; Xie, Xianrong; Zhu, Qinlong; Tang, Huiwu; Li, Qing; Chen, Letian; Liu, Yao-Guang

    2017-11-03

    Hybrids between divergent populations commonly show hybrid sterility; this reproductive barrier hinders hybrid breeding of the japonica and indica rice (Oryza sativa L.) subspecies. Here we show that structural changes and copy number variation at the Sc locus confer japonica-indica hybrid male sterility. The japonica allele, Sc-j, contains a pollen-essential gene encoding a DUF1618-domain protein; the indica allele, Sc-i, contains two or three tandem-duplicated ~ 28-kb segments, each carrying an Sc-j-homolog with a distinct promoter. In Sc-j/Sc-i hybrids, the high-expression of Sc-i in sporophytic cells causes suppression of Sc-j expression in pollen and selective abortion of Sc-j-pollen, leading to transmission ratio distortion. Knocking out one or two of the three Sc-i copies by CRISPR/Cas9 rescues Sc-j expression and male fertility. Our results reveal the gene dosage-dependent allelic suppression as a mechanism of hybrid incompatibility, and provide an effective approach to overcome the reproductive barrier for hybrid breeding.

  16. 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.

  17. Surface instabilities in shock loaded granular media

    Science.gov (United States)

    Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.

    2017-12-01

    The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to

  18. Theory and models of material erosion and lifetime during plasma instabilities in a tokamak environment

    International Nuclear Information System (INIS)

    Hassanein, A.; Konkashbaev, I.

    1999-01-01

    Surface and structural damage to plasma-facing components (PFCs) due to the frequent loss of plasma confinement remains a serious problem for the tokamak reactor concept. The deposited plasma energy causes significant surface erosion, possible structural failure, and frequent plasma contamination. Surface damage consists of vaporization, spallation, and liquid splatter of metallic materials. Structural damage includes large temperature increases in structural materials and at the interfaces between surface coatings and structural members. To evaluate the lifetimes of plasma-facing materials and nearby components and to predict the various forms of damage that they experience, comprehensive models (contained in the HEIGHTS computer simulation package) are developed, integrated self-consistently, and enhanced. Splashing mechanisms such as bubble boiling and various liquid magnetohydrodynamic instabilities and brittle destruction mechanisms of nonmelting materials are being examined. The design requirements and implications of plasma-facing and nearby components are discussed, along with recommendations to mitigate and reduce the effects of plasma instabilities on reactor components

  19. 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.

  20. Reoperation for non-structural valvular dysfunction caused by pannus ingrowth in aortic valve prosthesis.

    Science.gov (United States)

    Oh, Se Jin; Park, Samina; Kim, Jun Sung; Kim, Kyung-Hwan; Kim, Ki Bong; Ahn, Hyuk

    2013-07-01

    The authors' clinical experience is presented of non-structural valvular dysfunction of the prosthetic aortic valve caused by pannus ingrowth during the late postoperative period after previous heart valve surgery. Between January 1999 and April 2012, at the authors' institution, a total of 33 patients underwent reoperation for increased mean pressure gradient of the prosthetic aortic valve. All patients were shown to have pannus ingrowth. The mean interval from the previous operation was 16.7 +/- 4.3 years, and the most common etiology for the previous aortic valve replacement (AVR) was rheumatic valve disease. The mean effective orifice area index (EOAI) of the previous prosthetic valve was 0.97 +/- 0.11 cm2/m2, and the mean pressure gradient on the aortic prosthesis before reoperation was 39.1 +/- 10.7 mmHg. Two patients (6.1%) died in-hospital, and late death occurred in six patients (18.2%). At the first operation, 30 patients underwent mitral or tricuspid valve surgery as a concomitant procedure. Among these operations, mitral valve replacement (MVR) was combined in 24 of all 26 patients with rheumatic valve disease. Four patients underwent pannus removal only while the prosthetic aortic valve was left in place. The mean EOAI after reoperation was significantly increased to 1.16 +/- 0.16 cm2/m2 (p pannus ingrowth was shown in patients with a small EOAI of the prosthetic aortic valve and combined MVR for rheumatic disease. As reoperation for pannus overgrowth showed good clinical outcomes, an aggressive resection of pannus and repeated AVR should be considered in symptomatic patients to avoid the complications of other cardiac diseases.

  1. Imaging findings in posterior instability of the shoulder

    International Nuclear Information System (INIS)

    Harish, Srinivasan; Rebello, Ryan; O'Neill, John; Nagar, Arpit; Moro, Jaydeep; Pugh, David

    2008-01-01

    Posterior shoulder instability refers to the symptoms and signs resulting from excessive posterior translation of the humerus. Magnetic resonance (MR) imaging is the radiological modality of choice in the diagnostic assessment of posterior instability. Computed tomography (CT) is useful in the evaluation of osseous abnormalities associated with posterior instability. A detailed description of the posterior osseous and labroligamentous abnormalities has evolved recently, and many variant lesions of the posteroinferior labrum and/or capsular structures have been described. As the recommended surgical management of lesions associated with posterior instability is a lesion-specific approach, awareness of the specific lesions that have been described in association with posterior instability helps in pre-surgical planning. The purpose of this article is to review the classification of, and injury mechanisms leading to, posterior shoulder instability and to describe imaging findings associated with posterior instability, with emphasis on MR imaging. (orig.)

  2. Imaging findings in posterior instability of the shoulder

    Energy Technology Data Exchange (ETDEWEB)

    Harish, Srinivasan; Rebello, Ryan; O' Neill, John [St. Joseph' s Healthcare, Department of Diagnostic Imaging, Hamilton, ON (Canada); McMaster University, Faculty of Health Sciences, Hamilton (Canada); Nagar, Arpit [St. Joseph' s Healthcare, Department of Diagnostic Imaging, Hamilton, ON (Canada); Moro, Jaydeep [St. Joseph' s Healthcare, Department of Orthopedic Surgery, Hamilton, ON (Canada); McMaster University, Faculty of Health Sciences, Hamilton (Canada); Pugh, David [Brantford General Hospital, Department of Orthopedic Surgery, Brantford, ON (Canada)

    2008-08-15

    Posterior shoulder instability refers to the symptoms and signs resulting from excessive posterior translation of the humerus. Magnetic resonance (MR) imaging is the radiological modality of choice in the diagnostic assessment of posterior instability. Computed tomography (CT) is useful in the evaluation of osseous abnormalities associated with posterior instability. A detailed description of the posterior osseous and labroligamentous abnormalities has evolved recently, and many variant lesions of the posteroinferior labrum and/or capsular structures have been described. As the recommended surgical management of lesions associated with posterior instability is a lesion-specific approach, awareness of the specific lesions that have been described in association with posterior instability helps in pre-surgical planning. The purpose of this article is to review the classification of, and injury mechanisms leading to, posterior shoulder instability and to describe imaging findings associated with posterior instability, with emphasis on MR imaging. (orig.)

  3. Pressure-anisotropy-induced nonlinearities in the kinetic magnetorotational instability

    Science.gov (United States)

    Squire, J.; Quataert, E.; Kunz, M. W.

    2017-12-01

    In collisionless and weakly collisional plasmas, such as hot accretion flows onto compact objects, the magnetorotational instability (MRI) can differ significantly from the standard (collisional) MRI. In particular, pressure anisotropy with respect to the local magnetic-field direction can both change the linear MRI dispersion relation and cause nonlinear modifications to the mode structure and growth rate, even when the field and flow perturbations are very small. This work studies these pressure-anisotropy-induced nonlinearities in the weakly nonlinear, high-ion-beta regime, before the MRI saturates into strong turbulence. Our goal is to better understand how the saturation of the MRI in a low-collisionality plasma might differ from that in the collisional regime. We focus on two key effects: (i) the direct impact of self-induced pressure-anisotropy nonlinearities on the evolution of an MRI mode, and (ii) the influence of pressure anisotropy on the `parasitic instabilities' that are suspected to cause the mode to break up into turbulence. Our main conclusions are: (i) The mirror instability regulates the pressure anisotropy in such a way that the linear MRI in a collisionless plasma is an approximate nonlinear solution once the mode amplitude becomes larger than the background field (just as in magnetohyrodynamics). This implies that differences between the collisionless and collisional MRI become unimportant at large amplitudes. (ii) The break up of large-amplitude MRI modes into turbulence via parasitic instabilities is similar in collisionless and collisional plasmas. Together, these conclusions suggest that the route to magnetorotational turbulence in a collisionless plasma may well be similar to that in a collisional plasma, as suggested by recent kinetic simulations. As a supplement to these findings, we offer guidance for the design of future kinetic simulations of magnetorotational turbulence.

  4. Sheared Electroconvective Instability

    Science.gov (United States)

    Kwak, Rhokyun; Pham, Van Sang; Lim, Kiang Meng; Han, Jongyoon

    2012-11-01

    Recently, ion concentration polarization (ICP) and related phenomena draw attention from physicists, due to its importance in understanding electrochemical systems. Researchers have been actively studying, but the complexity of this multiscale, multiphysics phenomenon has been limitation for gaining a detailed picture. Here, we consider electroconvective(EC) instability initiated by ICP under pressure-driven flow, a scenario often found in electrochemical desalinations. Combining scaling analysis, experiment, and numerical modeling, we reveal unique behaviors of sheared EC: unidirectional vortex structures, its size selection and vortex propagation. Selected by balancing the external pressure gradient and the electric body force, which generates Hagen-Poiseuille(HP) flow and vortical EC, the dimensionless EC thickness scales as (φ2 /UHP)1/3. The pressure-driven flow(or shear) suppresses unfavorably-directed vortices, and simultaneously pushes favorably-directed vortices with constant speed, which is linearly proportional to the total shear of HP flow. This is the first systematic characterization of sheared EC, which has significant implications on the optimization of electrodialysis and other electrochemical systems.

  5. Using particle tracking to measure flow instabilities in an undergraduate laboratory experiment

    Science.gov (United States)

    Kelley, Douglas H.; Ouellette, Nicholas T.

    2011-03-01

    Much of the drama and complexity of fluid flow occurs because its governing equations lack unique solutions. The observed behavior depends on the stability of the multitude of solutions, which can change with the experimental parameters. Instabilities cause sudden global shifts in behavior. We have developed a low-cost experiment to study a classical fluid instability. By using an electromagnetic technique, students drive Kolmogorov flow in a thin fluid layer and measure it quantitatively with a webcam. They extract positions and velocities from movies of the flow using Lagrangian particle tracking and compare their measurements to several theoretical predictions, including the effect of the drive current, the spatial structure of the flow, and the parameters at which instability occurs. The experiment can be tailored to undergraduates at any level or to graduate students by appropriate emphasis on the physical phenomena and the sophisticated mathematics that govern them.

  6. Theoretical aspects of some collective instabilities in high-energy particle storage rings

    International Nuclear Information System (INIS)

    Ruggiero, F.

    1986-01-01

    After an introduction to single-particle dynamics, based on a unified Hamiltonian treatment of betatron and synchrotron oscillations, we consider two examples of collective instabilities which can limit the performances of high-energy storage rings: the transverse mode coupling instability, due to wake fields, and the incoherent beam-beam instability. Special emphasis is placed on the localization of the interactions between particles and surrounding structures, such as the accelerating RF cavities. We derive an exact invariant for the linearized synchrotron motion and, starting from the Vlasov equation, we discuss the coherent synchro-betatron resonances caused by localized impedance. Under suitable assumptions, we show that the effect of the beam-beam kicks in electron-positron machines can be described by new diffusive terms in a ''renormalized'' Fokker-Planck equation and is therefore equivalent to an additional source of noise for the betatron oscillations. (orig.)

  7. Methylene Blue Is Effective to Reverse Refractory Hemodynamic Instability due to Dimethoate Poisoning

    Directory of Open Access Journals (Sweden)

    Nick Youssefi

    2015-09-01

    Conclusion:MB treatment was effective to reverse hypotension and restore hemodynamic instability caused by dimethoate poisoning. This index case may pave way to further investigation of MB therapy for OP-induced hemodynamic instabilities.

  8. Relativistic gravitational instabilities

    International Nuclear Information System (INIS)

    Schutz, B.F.

    1987-01-01

    The purpose of these lectures is to review and explain what is known about the stability of relativistic stars and black holes, with particular emphases on two instabilities which are due entirely to relativistic effects. The first of these is the post-Newtonian pulsational instability discovered independently by Chandrasekhar (1964) and Fowler (1964). This effectively ruled out the then-popular supermassive star model for quasars, and it sets a limit to the central density of white dwarfs. The second instability was also discovered by Chandrasekhar (1970): the gravitational wave induced instability. This sets an upper bound on the rotation rate of neutron stars, which is near that of the millisecond pulsar PSR 1937+214, and which is beginning to constrain the equation of state of neutron matter. 111 references, 5 figures

  9. Character of decay instability

    International Nuclear Information System (INIS)

    Polovin, R.V.; Demutskii, V.P.

    1981-01-01

    If the initial wave is unstable in the upper half plane Im ω>0 and there are no branch points of the quasiwave number, or if waves traveling in the same direction coalesce at a branch point, the instability is convective. On the other hand, if a branch point k(ω) does exist in the upper half-plane Im ω>0, and not all the waves that merge at this point travel in the same direction, the instability is absolute. A Green's function that describes the evolution of the perturbations of the initial wave in space and in time is constructed. The growth rates of the decay instability of the harmonics are determined. The produced waves are richer in harmonics than the initial waves. It is shown that the decay instability of an Alfven wave is absolute

  10. Predicting the impact of Lynch syndrome-causing missense mutations from structural calculations

    DEFF Research Database (Denmark)

    Nielsen, Sofie V,; Stein, Amelie; Dinitzen, Alexander B.

    2017-01-01

    selected the human mismatch repair protein, MSH2, where missense variants are known to cause the hereditary cancer predisposition disease, known as Lynch syndrome. We show that the majority of disease-causing MSH2 mutations give rise to folding defects and proteasome-dependent degradation rather than...... and for diagnosis of Lynch syndrome, and perhaps other hereditary diseases....

  11. Genomic instability and radiation

    Energy Technology Data Exchange (ETDEWEB)

    Little, John B [Harvard School of Public Health, Boston, MA 02115 (United States)

    2003-06-01

    Genomic instability is a hallmark of cancer cells, and is thought to be involved in the process of carcinogenesis. Indeed, a number of rare genetic disorders associated with a predisposition to cancer are characterised by genomic instability occurring in somatic cells. Of particular interest is the observation that transmissible instability can be induced in somatic cells from normal individuals by exposure to ionising radiation, leading to a persistent enhancement in the rate at which mutations and chromosomal aberrations arise in the progeny of the irradiated cells after many generations of replication. If such induced instability is involved in radiation carcinogenesis, it would imply that the initial carcinogenic event may not be a rare mutation occurring in a specific gene or set of genes. Rather, radiation may induce a process of instability in many cells in a population, enhancing the rate at which the multiple gene mutations necessary for the development of cancer may arise in a given cell lineage. Furthermore, radiation could act at any stage in the development of cancer by facilitating the accumulation of the remaining genetic events required to produce a fully malignant tumour. The experimental evidence for such induced instability is reviewed. (review)

  12. Genomic instability and radiation

    International Nuclear Information System (INIS)

    Little, John B

    2003-01-01

    Genomic instability is a hallmark of cancer cells, and is thought to be involved in the process of carcinogenesis. Indeed, a number of rare genetic disorders associated with a predisposition to cancer are characterised by genomic instability occurring in somatic cells. Of particular interest is the observation that transmissible instability can be induced in somatic cells from normal individuals by exposure to ionising radiation, leading to a persistent enhancement in the rate at which mutations and chromosomal aberrations arise in the progeny of the irradiated cells after many generations of replication. If such induced instability is involved in radiation carcinogenesis, it would imply that the initial carcinogenic event may not be a rare mutation occurring in a specific gene or set of genes. Rather, radiation may induce a process of instability in many cells in a population, enhancing the rate at which the multiple gene mutations necessary for the development of cancer may arise in a given cell lineage. Furthermore, radiation could act at any stage in the development of cancer by facilitating the accumulation of the remaining genetic events required to produce a fully malignant tumour. The experimental evidence for such induced instability is reviewed. (review)

  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. Instability and Change in Collective Bargaining

    DEFF Research Database (Denmark)

    Brandl, Bernd; Ibsen, Christian Lyhne

    2017-01-01

    Previous studies on collective bargaining structures and macroeconomic performance have largely ignored the role of stable and instable institutional structures and the effects of institutional change itself. In this article we posit that institutional stability of collective bargaining is of maj...... following the change. This effect also holds for changes in both decentralization and centralization of institutions....

  15. [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.

  16. Damage-induced tensile instability

    International Nuclear Information System (INIS)

    Hult, J.

    1975-01-01

    The paper presents a unified description of ductile and brittle rupture phenomena in structural components under tensile loading with particular emphasis on creep rupture. Two structural elements are analyzed in detail: 1) the uniform tensile bar subject to a Heaviside history of tensile force and superimposed such loadings, i.e. staircase histories, and 2) the thinwalled spherical pressure vessel subject to a Heaviside history of internal pressure. For both these structures the conditions for instantaneous as well as delayed rupture are analysed. It is shown that a state of mechanical instability will be reached at a certain load or after a certain time. The cases of purely ductile rupture and purely brittle fracture are identified as two limiting cases of this general instability phenomenon. The Kachanov-Rabotnov damage law implies that a structural component will fail in tension only when it has reached a state of complete damage, i.e. zero load carrying capacity. The extended law predicts failure at an earlier stage of the deterioration process and is therefore more compatible with experimental observation. Further experimental support is offered by predictions for staircase loading histories, both step-up and step-down type. The presented damage theory here predicts strain histories which are in closer agreement with test data than predictions based on other phenomenological theories

  17. [Atrial fibrillation as consequence and cause of structural changes of atria].

    Science.gov (United States)

    Aparina, O P; Chikhireva, L N; Stukalova, O V; Mironova, N A; Kashtanova, S Iu; Ternovoĭ, S K; Golitsyn, S P

    2014-01-01

    Changes of atrial structure and function are the contributors of atrial fibrillation clinical course, complications and treatment effectiveness. Effects of inflammation and mechanical stretch on atrial structural remodeling leading to atrial fibrillation are reviewed in the article. Contemporary invasive and non-invasive methods of evaluation (including late gadolinium enhancement magnetic resonance imaging) of patients with atrial structural remodeling in atrial fibrillation are also described.

  18. Kinetic simulations of Rayleigh-Taylor instabilities

    International Nuclear Information System (INIS)

    Sagert, Irina; Bauer, Wolfgang; Colbry, Dirk; Howell, Jim; Staber, Alec; Strother, Terrance

    2014-01-01

    We report on an ongoing project to develop a large scale Direct Simulation Monte Carlo code. The code is primarily aimed towards applications in astrophysics such as simulations of core-collapse supernovae. It has been tested on shock wave phenomena in the continuum limit and for matter out of equilibrium. In the current work we focus on the study of fluid instabilities. Like shock waves these are routinely used as test-cases for hydrodynamic codes and are discussed to play an important role in the explosion mechanism of core-collapse supernovae. As a first test we study the evolution of a single-mode Rayleigh-Taylor instability at the interface of a light and a heavy fluid in the presence of a gravitational acceleration. To suppress small-wavelength instabilities caused by the irregularity in the separation layer we use a large particle mean free path. The latter leads to the development of a diffusion layer as particles propagate from one fluid into the other. For small amplitudes, when the instability is in the linear regime, we compare its position and shape to the analytic prediction. Despite the broadening of the fluid interface we see a good agreement with the analytic solution. At later times we observe the development of a mushroom like shape caused by secondary Kelvin-Helmholtz instabilities as seen in hydrodynamic simulations and consistent with experimental observations.

  19. Upgrade of Coastal Defence Structures Against Increased Loadings Caused by Climate Change

    DEFF Research Database (Denmark)

    Burcharth, Hans F.; Andersen, Thomas Lykke; Lara, Javier L.

    2014-01-01

    The paper presents a design exercise of upgrading a typical rock armoured revetment by modifying the structure profile and adding structure elements. Several concepts of upgrading are examined. A sea level rise corresponding to the mean of the IPCC 2007 predictions is used together with a slight ...

  20. 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

  1. 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...

  2. The Analysis and Structuring of the Causes Impeding the Introduction of Advanced Technologies for Exchange Grain Trading

    Directory of Open Access Journals (Sweden)

    Vinnychenko Olena V

    2015-03-01

    Full Text Available In the article the main causes impeding the development and introduction of advanced technologies for grain trading on commodity exchanges in Ukraine have been identified and structured. The generalization of existing shortcomings in operation of the domestic commodity exchanges has served the basis for the model, within which there were built: a directed graph of correlations between the above mentioned shortcomings in the operation of exchanges, the matrix of dependency and reachability. The causes have been identified and structured, the main ones being determined, which, in turn, makes it possible to carry out the correct sequence of actions and emphasize the primary issues requiring priority solutions at making management decisions in order to promote the grain exchange market. The suggested approach clearly shows the correlation between the existing causes and sequence of their elimination.

  3. Plasma physics and instabilities

    International Nuclear Information System (INIS)

    Lashmore-Davies, C.N.

    1981-01-01

    These lectures procide an introduction to the theory of plasmas and their instabilities. Starting from the Bogoliubov, Born, Green, Kirkwood, and Yvon (BBGKY) hierarchy of kinetic equations, the additional concept of self-consistent fields leads to the fundamental Vlasov equation and hence to the warm two-fluid model and the one-fluid MHD, or cold, model. The properties of small-amplitude waves in magnetized (and unmagnetized) plasmas, and the instabilities to which they give rise, are described in some detail, and a complete chapter is devoted to Landau damping. The linear theory of plasma instabilities is illustrated by the current-driven electrostatic kind, with descriptions of the Penrose criterion and the energy principle of ideal MHD. There is a brief account of the application of feedback control. The non-linear theory is represented by three examples: quasi-linear velocity-space instabilities, three-wave instabilities, and the stability of an arbitrarily largeamplitude wave in a plasma. (orig.)

  4. Cell structures caused by settling particles in turbulent Rayleigh-Bénard convection

    Science.gov (United States)

    Lee, Changhoon; Park, Sangro

    2016-11-01

    Turbulent thermal convection is an important phenomenon frequently found in nature and industrial processes, often with laden particles. In the last several decades, the vast majority of studies have addressed single phase convective flow with focus on the scaling relation of flow parameters associated with heat transfer. Particle-laden Rayleigh-Bénard convection, however, has not been sufficiently studied. In this study, modulation of cell structures by settling particles in turbulent Rayleigh-Bénard convection in a doubly periodic square channel is investigated using direct numerical simulation with a point particle approach. Flow parameters are fixed at Rayleigh number=106, Prandtl number=0.7, the aspect ratio=6, and Froude number=0.19. We report from the simulations that settling heavy particles modulate irregular large-scale thermal plume structures into organized polygonal cell structures. Different shapes of flow structures are obtained for different particle diameters and mass loadings. We found that polygonal cell structures arise due to asymmetric feedback force exerted by particles onto hot and cold plumes. Increasing the number of particles augments the asymmetry and the polygonal cell structures become smaller, eventually going to the hexagonal structures.

  5. Numerical modelling of ground vibration caused by elevated high-speed railway lines considering structure-soil-structure interaction

    DEFF Research Database (Denmark)

    Bucinskas, Paulius; Andersen, Lars Vabbersgaard; Persson, Kent

    2016-01-01

    Construction of high speed railway lines has been an increasing trend in recent years. Countries like Denmark and Sweden plan to expand and upgrade their railways to accommodate high-speed traffic. To benefit from the full potential of the reduced commuting times, these lines must pass through...... densely populated urban areas with the collateral effect of increased noise and vibrations levels. This paper aims to quantify the vibrations levels in the area surrounding an elevated railway line built as a multi-span bridge structure. The proposed model employs finite-element analysis to model......-space. The paper analyses the effects of structure-soil-structure interaction on the dynamic behaviour of the surrounding soil surface. The effects of different soil stratification and material properties as well as different train speeds are assessed. Finally, the drawbacks of simplifying the numerical model...

  6. Structural response of a Tokamak first wall under electromagnetic forces caused by a plasma disruption

    International Nuclear Information System (INIS)

    Crutzen, Y.R.; Biggio, M.; Farfaletti-Casali, F.; Antonacci, P.; Vitali, R.

    1987-01-01

    The modern computerized techniques of CAD/FEM analysis are extensively applied for the numerical simulation of the electromagnetic-mechanical coupling induced in the last design configuration of NET first wall during a plasma disruption event. A picture of the impact of the electromagnetic forces on the structural behaviour of the outboard DN first wall is presented an an improvement of the FW structural section is proposed. In any case, additional investigations will be performed during the long process of structural behaviour optimization of the first wall reactor components

  7. Numerical analysis of free surface instabilities in the IFMIF lithium target

    International Nuclear Information System (INIS)

    Gordeev, S.; Heinzel, V.; Moeslang, A.

    2007-01-01

    The International Fusion Materials Facility (IFMIF) facility uses a high speed (10-20 m/s) Lithium (Li) jet flow as a target for two 40 MeV/125 mA deuteron beams. The major function of the Li target is to provide a stable Li jet for the production of an intense neutron flux. For the understanding the lithium jet behaviour and elimination of the free-surface flow instabilities a detailed analysis of the Li jet flow is necessary. Different kinds of instability mechanisms in the liquid jet flow have been evaluated and classified based on analytical and experimental data. Numerical investigations of the target free surface flow have been performed. Previous numerical investigations have shown in principle the suitability of CFD code Star- CD for the simulation of the Li-target flow. The main objective of this study is detailed numerical analysis of instabilities in the Li-jet flow caused by boundary layer relaxation near the nozzle exit, transition to the turbulence flow and back wall curvature. A number of CFD models are developed to investigate the formation of instabilities on the target surface. Turbulence models are validated on the experimental data. Experimental observations have shown that the change of the nozzle geometry at the outlet such as a slight divergence of the nozzle surfaces or nozzle edge defects causes the flow separation and occurrence of longitudinal periodic structures on the free surface with an amplitude up to 5 mm. Target surface fluctuations of this magnitude can lead to the penetration of the deuteron beam in the target structure and cause the local overheating of the back plat. Analysis of large instabilities in the Li-target flow combined with the heat distribution in lithium depending on the free surface shape is performed in this study. (orig.)

  8. Age and cause mortality structure in the Italian regions at the beginning of the health transition: a research

    Directory of Open Access Journals (Sweden)

    Lorenzo Del Panta

    2013-05-01

    Full Text Available This paper aims at exploring Italian mortality structure (by age and cause of death at the regional level in the last decades of the 19th Century. These years, corresponding to the beginning of the health transition process, were crucial in the Italian experience. The analysis is based on a careful exploitation of the volume “Statistica delle cause delle morti 1888”, published in 1890, by the General Directorate of Statistics. This volume is the only one which offers for the Italian regions, before the second World war, death statistics classified according to both age and cause together. The principal objectives of this descriptive contribution are essentially to illustrate the territorial variation of mortality conditions in the first phase of the health transition process as well as to underline the relevance and the complexities of the causes specific mortality analysis to explain the geographical mortality differentials in terms of age and sex.

  9. Causes and consequences of personal financial management in the case of larger and structural charitable donations

    NARCIS (Netherlands)

    Wiepking, P.; Bekkers, R.H.F.P.

    2010-01-01

    We study causes and consequences of financial management in households in the specific case of charitable giving. We test hypotheses using couples in the Giving in the Netherlands Panel Study (n = 1,101). We find that more relationship specific investments lead to deciding on charitable giving as

  10. 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.

  11. Fingerprints of dynamical instabilities

    International Nuclear Information System (INIS)

    Chomaz, Ph.; Colonna, M.; Guarnera, A.

    1993-01-01

    It is explained why any reduced descriptions, such as mean field approximation, are stochastic in nature. It is shown that the introduction of this stochastic dynamics leads to a predictive theory in a statistical sens whatever the individual trajectories are characterized by the occurrence of bifurcations, instabilities or phase transitions. Concerning nuclear matter, the spinodal instability is discussed. In such a critical situation, the possibility to replace the stochastic part of the collision integral in the Boltzmann-Langevin model by the numerical noise associated with the finite number of test particles in ordinary BUU treatment is studied. It is shown that the fingerprints of these instabilities are kept during the evolution because of the relatively long recombination time compared with the typical time scales imposed by the Coulomb repulsion and the possible collective expansion. (author) 5 refs., 12 figs

  12. Instability and star evolution

    International Nuclear Information System (INIS)

    Mirzoyan, L.V.

    1981-01-01

    The observational data are discussed which testify that the phenomena of dynamical instability of stars and stellar systems are definite manifestations of their evolution. The study of these phenomena has shown that the instability is a regular phase of stellar evolution. It has resulted in the recognition of the most important regularities of the process of star formation concerning its nature. This became possible due to the discovery in 1947 of stellar associations in our Galaxy. The results of the study of the dynamical instability of stellar associations contradict the predictions of classical hypothesis of stellar condensation. These data supplied a basis for a new hypothesis on the formation of stars and nebulae by the decay of superdense protostars [ru

  13. Observation of the ion resonance instability

    International Nuclear Information System (INIS)

    Peurrung, A.J.; Notte, J.; Fajans, J.

    1993-01-01

    Observation of the ion resonance instability in a pure electron plasma trap contaminated with a small population of ions is reported. The ion population is maintained by ionization of the background gas. The instability causes the plasma to move steadily off-center while undergoing l=1 diocotron oscillations. The observed scaling of the maximum growth point is presented, and the growth rate and its dependence on ion density are discussed. Several aspects of the observed behavior are not in agreement with previous theory but derive from the transitory nature of the ion population

  14. Self-Induced Faraday Instability Laser

    Science.gov (United States)

    Perego, A. M.; Smirnov, S. V.; Staliunas, K.; Churkin, D. V.; Wabnitz, S.

    2018-05-01

    We predict the onset of self-induced parametric or Faraday instabilities in a laser, spontaneously caused by the presence of pump depletion, which leads to a periodic gain landscape for light propagating in the cavity. As a result of the instability, continuous wave oscillation becomes unstable even in the normal dispersion regime of the cavity, and a periodic train of pulses with ultrahigh repetition rate is generated. Application to the case of Raman fiber lasers is described, in good quantitative agreement between our conceptual analysis and numerical modeling.

  15. The Syndemic of Opioid Misuse, Overdose, HCV, and HIV: Structural-Level Causes and Interventions.

    Science.gov (United States)

    Perlman, David C; Jordan, Ashly E

    2018-04-01

    This article reviews the case for recognizing (1) the epidemics of opioid misuse, overdose, hepatitis C virus, and HIV as a syndemic and (2) the importance of examining and addressing structural factors in responses to this syndemic. We focus on the current syndemic in the US, but also consider data from other locations to highlight the issues existing and arising in various contexts. Advances in multi-level theory and statistical methods allow sound ecologic and multi-level analyses of the impact of structural factors on the syndemic. Studies of opioid misuse, overdoses, hepatitis C virus, and HIV demonstrate that area-level access to healthcare, medication-assisted treatment of opioid use disorders, sterile injection equipment, and overdose prevention with naloxone, as well as factors such as opioid marketing, income inequality, intensity of policing activities, and health care policies, are related to the prevalence of substance misuse, overdoses, infection risk, and morbidity. Structural variables can predict area-level vulnerability to the syndemic. The implementation of combined prevention and treatment interventions can control and reverse components of the syndemic. Recognizing and monitoring potent structural factors can facilitate the identification of areas at risk of vulnerability to the syndemic. Further, many structural factors are modifiable through intervention and policy to reduce structural vulnerability and create health-enabling environments. Evidence supports the immediate implementation of broader HCV and HIV testing and substance use screening, medication-assisted treatment, needle/syringe exchange programs, naloxone programs, increased population-level implementation of HCV treatment, and further attention to structural-level factors predicting, and contributing to, area-level vulnerability, such as degrees of opioid marketing, distribution, and prescribing.

  16. RINGED ACCRETION DISKS: INSTABILITIES

    Energy Technology Data Exchange (ETDEWEB)

    Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

    2016-04-01

    We analyze the possibility that several instability points may be formed, due to the Paczyński mechanism of violation of mechanical equilibrium, in the orbiting matter around a supermassive Kerr black hole. We consider a recently proposed model of a ringed accretion disk, made up by several tori (rings) that can be corotating or counter-rotating relative to the Kerr attractor due to the history of the accretion process. Each torus is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. We prove that the number of the instability points is generally limited and depends on the dimensionless spin of the rotating attractor.

  17. Changes in proteasome structure and function caused by HAMLET in tumor cells.

    Science.gov (United States)

    Gustafsson, Lotta; Aits, Sonja; Onnerfjord, Patrik; Trulsson, Maria; Storm, Petter; Svanborg, Catharina

    2009-01-01

    Proteasomes control the level of endogenous unfolded proteins by degrading them in the proteolytic core. Insufficient degradation due to altered protein structure or proteasome inhibition may trigger cell death. This study examined the proteasome response to HAMLET, a partially unfolded protein-lipid complex, which is internalized by tumor cells and triggers cell death. HAMLET bound directly to isolated 20S proteasomes in vitro and in tumor cells significant co-localization of HAMLET and 20S proteasomes was detected by confocal microscopy. This interaction was confirmed by co-immunoprecipitation from extracts of HAMLET-treated tumor cells. HAMLET resisted in vitro degradation by proteasomal enzymes and degradation by intact 20S proteasomes was slow compared to fatty acid-free, partially unfolded alpha-lactalbumin. After a brief activation, HAMLET inhibited proteasome activity in vitro and in parallel a change in proteasome structure occurred, with modifications of catalytic (beta1 and beta5) and structural subunits (alpha2, alpha3, alpha6 and beta3). Proteasome inhibition was confirmed in extracts from HAMLET-treated cells and there were indications of proteasome fragmentation in HAMLET-treated cells. The results suggest that internalized HAMLET is targeted to 20S proteasomes, that the complex resists degradation, inhibits proteasome activity and perturbs proteasome structure. We speculate that perturbations of proteasome structure might contribute to the cytotoxic effects of unfolded protein complexes that invade host cells.

  18. Predicting the impact of Lynch syndrome-causing missense mutations from structural calculations.

    Directory of Open Access Journals (Sweden)

    Sofie V Nielsen

    2017-04-01

    Full Text Available Accurate methods to assess the pathogenicity of mutations are needed to fully leverage the possibilities of genome sequencing in diagnosis. Current data-driven and bioinformatics approaches are, however, limited by the large number of new variations found in each newly sequenced genome, and often do not provide direct mechanistic insight. Here we demonstrate, for the first time, that saturation mutagenesis, biophysical modeling and co-variation analysis, performed in silico, can predict the abundance, metabolic stability, and function of proteins inside living cells. As a model system, we selected the human mismatch repair protein, MSH2, where missense variants are known to cause the hereditary cancer predisposition disease, known as Lynch syndrome. We show that the majority of disease-causing MSH2 mutations give rise to folding defects and proteasome-dependent degradation rather than inherent loss of function, and accordingly our in silico modeling data accurately identifies disease-causing mutations and outperforms the traditionally used genetic disease predictors. Thus, in conclusion, in silico biophysical modeling should be considered for making genotype-phenotype predictions and for diagnosis of Lynch syndrome, and perhaps other hereditary diseases.

  19. Lower hybrid parametric instabilities nonuniform pump waves and tokamak applications

    International Nuclear Information System (INIS)

    Berger, R.L.; Chen, L.; Kaw, P.K.; Perkins, F.W.

    1976-11-01

    Electrostatic lower hybrid ''pump'' waves often launched into tokamak plasmas by structures (e.g., waveguides) whose dimensions are considerably smaller than characteristic plasma sizes. Such waves propagate in well-defined resonance cones and give rise to parametric instabilities driven by electron E x B velocities. The finite size of the resonance cone region determines the threshold for both convective quasimode decay instabilities and absolute instabilities. The excitation of absolute instabilities depends on whether a travelling or standing wave pump model is used; travelling wave pumps require the daughter waves to have a definite frequency shift. Altogether, parametric instabilities driven by E x B velocities occur for threshold fields significantly below the threshold for filamentation instabilities driven by pondermotive forces. Applications to tokamak heating show that nonlinear effects set in when a certain power-per-wave-launching port is exceeded

  20. MR imaging in sports-related glenohumeral instability

    International Nuclear Information System (INIS)

    Woertler, Klaus; Waldt, Simone

    2006-01-01

    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.)

  1. Structural and functional analysis of the ASM p.Ala359Asp mutant that causes acid sphingomyelinase deficiency.

    Science.gov (United States)

    Acuña, Mariana; Castro-Fernández, Víctor; Latorre, Mauricio; Castro, Juan; Schuchman, Edward H; Guixé, Victoria; González, Mauricio; Zanlungo, Silvana

    2016-10-21

    Niemann-Pick disease (NPD) type A and B are recessive hereditary disorders caused by deficiency in acid sphingomyelinase (ASM). The p.Ala359Asp mutation has been described in several patients but its functional and structural effects in the protein are unknown. In order to characterize this mutation, we modeled the three-dimensional ASM structure using the recent available crystal of the mammalian ASM as a template. We found that the p.Ala359Asp mutation is localized in the hydrophobic core and far from the sphingomyelin binding site. However, energy function calculations using statistical potentials indicate that the mutation causes a decrease in ASM stability. Therefore, we investigated the functional effect of the p.Ala359Asp mutation in ASM expression, secretion, localization and activity in human fibroblasts. We found a 3.8% residual ASM activity compared to the wild-type enzyme, without changes in the other parameters evaluated. These results support the hypothesis that the p.Ala359Asp mutation causes structural alterations in the hydrophobic environment where ASM is located, decreasing its enzymatic activity. A similar effect was observed in other previously described NPDB mutations located outside the active site of the enzyme. This work shows the first full size ASM mutant model describe at date, providing a complete analysis of the structural and functional effects of the p.Ala359Asp mutation over the stability and activity of the enzyme. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Microbunch Instability Theory and Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Stupakov, G.

    2005-01-26

    Over the last years there have been several reports of quasiperiodic bursts of coherent synchrotron radiation (CSR) in electron rings in the microwave and far-infrared range. The observations were made on synchrotron radiation light sources which include the Synchrotron Ultraviolet Radiation Facility SURF II [1], the VUV ring at the National Synchrotron Light Source at BNL [2, 3], second generation light sources MAX-I [4], BESSY II [5], and ALS [6]. General features of those observations can be summarized as follows. Above a threshold current, there is a strongly increased radiation of the beam in the range of wavelengths shorter than the bunch length, {lambda} < {sigma}{sub 2}. At large currents, this radiation is observed as a sequence of random bursts. In the bursting regime, intensity of the radiation scales approximately as square of the number of particles in the bunch, indicating a coherent nature of the phenomenon. It is generally accepted that the source of this radiation is related to the microbunching of the beam arising from development of a microwave instability caused by the coherent synchrotron radiation of the beam. A relativistic electron beam moving in a circular orbit in free space can radiate coherently if the wavelength of the synchrotron radiation exceeds the length of the bunch. In accelerators coherent radiation of the bunch is usually suppressed by the shielding effect of the conducting walls of the vacuum chamber [7-9], which gives an exponential cutoff of wavelengths greater than a certain threshold. However, an initial density fluctuation with a characteristic length much shorter than the shielding threshold would radiate coherently. If the radiation reaction force is such that it results in the growth of the initial fluctuation one can expect an instability that leads to micro-bunching of the beam and an increased coherent radiation at short wavelengths. A possibility of CSR instability was pointed out in Refs. [10, 11].

  3. Assessment of Flow Instability in Passive Auxiliary Feedwater System (PAFS) Using RELAP5

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Seong-Su; Hong, Soon-Joon [FNC Tech., Yongin (Korea, Republic of); Cheon, Jong; Kim, Han-Gon [KHNP, Daejeon (Korea, Republic of)

    2015-10-15

    In this study, the occurrence possibility of both instabilities in PAFS is assessed with the best-estimate thermal hydraulic code, RELAP5. From the RELAP5 code analysis, the Ledinegg instability might not occur in PAFS. The DWO might occur in PAFS but the effect of the oscillation on the heat removal capacity of PAFS was not large. Therefore, it is concluded that PAFS is safe in terms of flow instabilities. Since PAFS is two-phase flow system, flow instabilities may occur. Flow instabilities may cause the severe deterioration of heat removal capability of PAFS due to the reduction of the condensate flow. For the reliable operation of PAFS, it is required to assess the flow instabilities in PAFS. The Ledinegg-type instability and the Density Wave Oscillation (DWO) are the representative static flow instability and the dynamic flow instability, respectively.

  4. Strings, vortex rings, and modes of instability

    Directory of Open Access Journals (Sweden)

    Steven S. Gubser

    2015-03-01

    Full Text Available We treat string propagation and interaction in the presence of a background Neveu–Schwarz three-form field strength, suitable for describing vortex rings in a superfluid or low-viscosity normal fluid. A circular vortex ring exhibits instabilities which have been recognized for many years, but whose precise boundaries we determine for the first time analytically in the small core limit. Two circular vortices colliding head-on exhibit stronger instabilities which cause splitting into many small vortices at late times. We provide an approximate analytic treatment of these instabilities and show that the most unstable wavelength is parametrically larger than a dynamically generated length scale which in many hydrodynamic systems is close to the cutoff. We also summarize how the string construction we discuss can be derived from the Gross–Pitaevskii Lagrangian, and also how it compares to the action for giant gravitons.

  5. Fluid Instabilities of Magnetar-Powered Supernovae

    Science.gov (United States)

    Chen, Ke-Jung

    2017-05-01

    Magnetar-powered supernova explosions are competitive models for explaining very luminous optical transits. Until recently, these explosion models were mainly calculated in 1D. Radiation emitted from the magnetar snowplows into the previous supernovae ejecta and causes a nonphysical dense shell (spike) found in previous 1D studies. This suggests that strong fluid instabilities may have developed within the magnetar-powered supernovae. Such fluid instabilities emerge at the region where luminous transits later occur, so they can affect the consequent observational signatures. We examine the magnetar-powered supernovae with 2D hydrodynamics simulations and find that the 1D dense shell transforms into the development of Rayleigh-Taylor and thin shell instabilities in 2D. The resulting mixing is able to fragment the entire shell and break the spherical symmetry of supernovae ejecta.

  6. Prediction of flow instability during natural convection

    International Nuclear Information System (INIS)

    Farhadi, Kazem

    2005-01-01

    The occurrence of flow excursion instability during passive heat removal for Tehran Research Reactor (TRR) has been analyzed at low-pressure and low-mass rate of flow conditions without boiling taking place. Pressure drop-flow rate characteristics in the general case are determined upon a developed code for this purpose. The code takes into account variations of different pressure drop components caused by different powers as well as different core inlet temperatures. The analysis revealed the fact that the instability can actually occur in the natural convection mode for a range of powers per fuel plates at a predetermined inlet temperature with fixed geometry of the core. Low mass rate of flow and high sub-cooling are the two important conditions for the occurrence of static instability in the TRR. The calculated results are compared with the existing data in the literature. (author)

  7. Irregular breakfast consumption in adolescence and the family environment: underlying causes by family structure.

    Science.gov (United States)

    Levin, Kate A; Kirby, Joanna

    2012-08-01

    Data from the 2002, 2006 and 2010 Scottish Health Behaviour in School-aged Children (HBSC) surveys were analysed using logistic multilevel regression for outcome variable irregular breakfast consumption (IBC). IBC prevalence in Scotland was higher among young people from reconstituted and single parent families, and particularly single father families. Family characteristics, found previously to be associated with breakfast consumption, such as number of siblings, perceived parenting, parental involvement and family affluence, differed by family structure. Family structure inequalities in IBC existed, also after adjustment for year and child's sex, age, grade and ethnicity. Across all family structures, IBC was more prevalent at the older age groups, among those who had difficult communication with their parents, and where household routines were infrequent. Greater number of siblings and lower family affluence were associated with higher odds of IBC in single mother and both parent families, while having a second home was associated with higher odds in reconstituted households. Fair parenting and being close to at least one parent was associated with reduced odds of IBC in single mother households, while being close to all parents was in single father households. In single mother homes, having a working mother was also positively associated with IBC. Family structure differences should be considered when addressing irregular breakfast consumption in adolescence. Copyright © 2012 Elsevier Ltd. All rights reserved.

  8. Earthworms (Aporrectodea spp.; Lumbricidae) cause soil structure problems in young Dutch polders

    NARCIS (Netherlands)

    Ester, A.; Rozen, van K.

    2002-01-01

    The presence of earthworms in relation to clay soil structure problems in arable fields in the Flevopolders (the Netherlands) was studied. Recently, farmers in this area have had difficulty in harvesting potatoes in predominantly wet years. After a dry period, soil particles in the top layer of the

  9. Structural morphology of alkali feldspars and zircon and oriented intergrowths causing asterism in gemstones

    NARCIS (Netherlands)

    Woensdregt, C.F.

    1990-01-01

    Crystalline material grown in aqueous solutions or from vapour phase is often bounded by plane crystal faces. The surface configuration of such faces, that is controlled by the internal crystal structure, can be derived by the Hartman-Perdok theory with atomic precision. The crystal faces can be

  10. Electron spin transition causing structure transformations of earth's interiors under high pressure

    Science.gov (United States)

    Yamanaka, T.; Kyono, A.; Kharlamova, S.; Alp, E.; Bi, W.; Mao, H.

    2012-12-01

    To elucidate the correlation between structure transitions and spin state is one of the crucial problems for understanding the geophysical properties of earth interiors under high pressure. High-pressure studies of iron bearing spinels attract extensive attention in order to understand strong electronic correlation such as the charge transfer, electron hopping, electron high-low spin transition, Jahn-Teller distortion and charge disproponation in the lower mantle or subduction zone [1]. Experiment Structure transitions of Fe3-xSixO4, Fe3-xTixO4 Fe3-xCrxO4 spinel solid solution have been investigated at high pressure up to 60 GPa by single crystal and powder diffraction studies using synchrotron radiation with diamond anvil cell. X-ray emission experiment (XES) at high pressure proved the spin transition of Fe-Kβ from high spin (HS) to intermediate spin state (IS) or low spin state (LS). Mössbauer experiment and Raman spectra study have been also conducted for deformation analysis of Fe site and confirmation of the configuration change of Fe atoms. Jahn-Teller effect A cubic-to-tetragonal transition under pressure was induced by Jahn-Teller effect of IVFe2+ (3d6) in the tetrahedral site of Fe2TiO4 and FeCr2O4, providing the transformation from 43m (Td) to 42m (D2d). Tetragonal phase is formed by the degeneracy of e orbital of Fe2+ ion. Their c/a ratios are c/adisordered in the M2 site. At pressures above 53 GPa, Fe2TiO4 structure further transforms to Pmma. This structure change results in the order-disorder transition [2]. New structure of Fe2SiO4 The spin transition exerts an influence to Fe2SiO4 spinel structure and triggers two distinct curves of the lattice constant in the spinel phase. The reversible structure transition from cubic to pseudo-rhombohedral phase was observed at about 45 GPa. This transition is induced by the 20% shrinkage of ionic radius of VIFe2+at the low sin state. Laser heating experiment at 1500 K has confirmed the decomposition from the

  11. Computational and Experimental Investigation of Liquid Propellant Rocket Combustion Instability

    Data.gov (United States)

    National Aeronautics and Space Administration — Combustion instability has been a problem faced by rocket engine developers since the 1940s. The complicated phenomena has been highly unpredictable, causing engine...

  12. Buneman instability and Pierce instability in a collisionless bounded plasma

    International Nuclear Information System (INIS)

    Iizuka, Satoru; Saeki, Koichi; Sato, Noriyoshi; Hatta, Yoshisuke

    1983-01-01

    A systematic experiment is performed on the Buneman instability and the Pierce instability in a bounded plasma consisting of beam electrons and stationary ions. Current fluctuations are confirmed to be induced by the Buneman instability. On the other hand, the Pierce instability gives rise to a current limitation. The phenomena are well explained by Mikhailovskii's theory taking account of ion motion in a bounded plasma. (author)

  13. Coherent Instabilities of ILC Damping Ring

    Energy Technology Data Exchange (ETDEWEB)

    Heifets, S.; Stupakov, G.; Bane, K.; /SLAC

    2006-09-27

    The paper presents the first attempt to estimates the ILC damping ring impedance and compare thresholds of the classical instabilities for several designs initially proposed for the DR. The work was carried out in the spring of 2006. Since then the choice of the DR is narrowed. Nevertheless, the analysis described may be useful for the next iterations of the beam stability. Overall, the conventional instabilities will have little impact on the ring performance provided the careful design of the ring minimizes the impedance below acceptable level indicated above. The only exception is the transverse CB instability. The longitudinal CB is less demanding. However, even the transverse CB instability would have threshold current above nominal provided the aperture in the wigglers is increased from 8 mm to 16 mm. The microwave instability needs more studies. Nevertheless, we should remember that the ILC DR is different from existing high-current machines at least in two respects: absence of the beam-beam tune spread stabilizing beams in colliders, and unusual strict requirements for low emittance. That may cause new problems such as bunch emittance dilution due to high-frequency wakes (BPMs, grooves), etc. Even if such a possibility exists, it probably universal for all machines and ought be addressed in the design of vacuum components rather than have effect on the choice of the machine design.

  14. Magnetohydrodynamic instability in annular linear induction pump

    International Nuclear Information System (INIS)

    Araseki, Hideo; Kirillov, Igor R.; Preslitsky, Gennady V.; Ogorodnikov, Anatoly P.

    2006-01-01

    In the previous work, the authors showed some detailed aspects of the magnetohydrodynamic instability arising in an annular linear induction pump: the instability is accompanied with a low frequency pressure pulsation in the range of 0-10 Hz when the magnetic Reynolds number is larger than unity; the low frequency pressure pulsation is produced by the sodium vortices that come from some azimuthal non-uniformity of the applied magnetic field or of the sodium inlet velocity. In the present work, an experiment and a numerical analysis are carried out to verify the pump winding phase shift that is expected as an effective way to suppress the instability. The experimental data shows that the phase shift suppresses the instability unless the slip value is so high, but brings about a decrease of the developed pressure. The numerical results indicate that the phase shift causes a local decrease of the electromagnetic force, which results in the suppression of the instability and the decrease of the developed pressure. In addition, it is exhibited that the intensity of the double-supply-frequency pressure pulsation is in nearly the same level in the case with and without the phase shift

  15. Adolescent patellar instability: current concepts review.

    Science.gov (United States)

    Clark, D; Metcalfe, A; Wogan, C; Mandalia, V; Eldridge, J

    2017-02-01

    Patellar instability most frequently presents during adolescence. Congenital and infantile dislocation of the patella is a distinct entity from adolescent instability and measurable abnormalities may be present at birth. In the normal patellofemoral joint an increase in quadriceps angle and patellar height are matched by an increase in trochlear depth as the joint matures. Adolescent instability may herald a lifelong condition leading to chronic disability and arthritis. Restoring normal anatomy by trochleoplasty, tibial tubercle transfer or medial patellofemoral ligament (MPFL) reconstruction in the young adult prevents further instability. Although these techniques are proven in the young adult, they may cause growth arrest and deformity where the physis is open. A vigorous non-operative strategy may permit delay of surgery until growth is complete. Where non-operative treatment has failed a modified MPFL reconstruction may be performed to maintain stability until physeal closure permits anatomical reconstruction. If significant growth remains an extraosseous reconstruction of the MPFL may impart the lowest risk to the physis. If minor growth remains image intensifier guided placement of femoral intraosseous fixation may impart a small, but acceptable, risk to the physis. This paper presents and discusses the literature relating to adolescent instability and provides a framework for management of these patients. Cite this article: Bone Joint J 2017;99-B:159-70. ©2017 The British Editorial Society of Bone & Joint Surgery.

  16. Structure of complications, causes of mortality, clinical and morphological parallels in acute poisoning with methadone hydrochloride

    OpenAIRE

    Andryuishchenko, V.V.; Kalish, N.M.; Kurdil, N.V.

    2018-01-01

    Background. The relevance of the study of methadone poisoning in Kyiv is determined by a significant increase in the number of poisonings among the population in recent years and high rates of mortality. The purpose of this study is to determine the factors that caused the fatal methadone poisonings in order to develop measures for reducing mortality among this category of patients. Materials and methods. The subject of the study is 35 cases of deaths due to the “street” methadone poisoning i...

  17. 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...

  18. Agricultural Markets Instability

    NARCIS (Netherlands)

    Garrido, A.; Brümmer, B.; M'Barek, R.; Gielen-Meuwissen, M.P.M.; Morales-Opazo, C.

    2016-01-01

    Since the financial and food price crises of 2007, market instability has been a topic of major concern to agricultural economists and policy professionals. This volume provides an overview of the key issues surrounding food prices volatility, focusing primarily on drivers, long-term implications of

  19. Comment on critical instability

    International Nuclear Information System (INIS)

    King, S.F.; Suzuki, Mahiko

    1992-01-01

    We discuss the problem of the mass splitting between top and bottom quarks, within the context of Nambu-Jona-Lasinio type models involving top and bottom quark condensates. We interpret the phenomenon of 'critical instability' recently proposed to account for such a mass splitting as the fine-tuning of two vacuum expectation values in a composite two-Higgs doublet model. (orig.)

  20. Rayleigh convective instability in the presence of phase transitions of water vapor. The formation of large-scale eddies and cloud structures

    International Nuclear Information System (INIS)

    Shmerlin, Boris Ya; Kalashnik, Maksim V

    2013-01-01

    Convective motions in moist saturated air are accompanied by the release of latent heat of condensation. Taking this effect into account, we consider the problem of convective instability of a moist saturated air layer, generalizing the formulation of the classical Rayleigh problem. An analytic solution demonstrating the fundamental difference between moist convection and Rayleigh convection is obtained. Upon losing stability in the two-dimensional case, localized convective rolls or spatially periodic chains of rollers with localized areas of upward motion evolve. In the case of axial symmetry, the growth of localized convective vortices with circulation characteristic of tropical cyclones (hurricanes) is possible at the early stages of development and on the scale of tornados to tropical cyclones. (methodological notes)

  1. Crystal structures of wild-type and mutated cyclophilin B that causes hyperelastosis cutis in the American quarter horse

    Directory of Open Access Journals (Sweden)

    Boudko Sergei P

    2012-11-01

    Full Text Available Abstract Background Hyperelastosis cutis is an inherited autosomal recessive connective tissue disorder. Affected horses are characterized by hyperextensible skin, scarring, and severe lesions along the back. The disorder is caused by a mutation in cyclophilin B. Results The crystal structures of both wild-type and mutated (Gly6->Arg horse cyclophilin B are presented. The mutation neither affects the overall fold of the enzyme nor impairs the catalytic site structure. Instead, it locally rearranges the flexible N-terminal end of the polypeptide chain and also makes it more rigid. Conclusions Interactions of the mutated cyclophilin B with a set of endoplasmic reticulum-resident proteins must be affected.

  2. Polarization singularities of optical fields caused by structural dislocations in crystals

    International Nuclear Information System (INIS)

    Savaryn, V; Vasylkiv, Yu; Krupych, O; Skab, I; Vlokh, R

    2013-01-01

    We analyze polarization singularities of optical beams that propagate through crystals possessing structural dislocations. We show that screw dislocations of crystalline structure can lead to the appearance of purely screw-type dislocations of light wavefronts. This can happen only in crystals that belong to trigonal and cubic systems. These polarization singularities will give rise to optical vortices with the topological charge equal to ±1, whenever a crystal sample is placed between crossed circular polarizers. We have also found that edge dislocations present in the cubic and trigonal crystals, with the Burgers vector perpendicular to the three-fold symmetry axes, can impose mixed screw-edge dislocations in the wavefronts of optical beams and generate singly charged optical vortices. The results of our analysis can be applied for detecting and identifying dislocations of different types available in crystals. (paper)

  3. Analysis of the Impact Caused by Coherent Structures in Swirling Flow Combustion Systems

    Directory of Open Access Journals (Sweden)

    Valera-Medina A.

    2012-04-01

    Full Text Available Amongst the technologies used in the energy and propulsion generation for the reduction of emissions, the use of swirling flows has demonstrated its high performance in anchoring the flame inside of the combustion systems. This, added to the use of premixing in the pre-chambers, has created one of the most innovative methods for the reduction of highly polluting particles such as NOx. However, the lack of understanding of these flows makes it necessary to increase the research on the topic in order to clarify themes as complex as the role of the coherent structures inside of the system. This paper explains some of the phenomena produced by some of the coherent structures observed in the system. The results showed the existence of complex Recirculation Zones (RZ, Precessing Vortex Core (PVC and Combustion Induced Vortex Breakdown (CIVB.

  4. Nur77 forms novel nuclear structures upon DNA damage that cause transcriptional arrest

    International Nuclear Information System (INIS)

    Leseleuc, Louis de; Denis, Francois

    2006-01-01

    The orphan nuclear receptor Nur77 has been implicated in both growth and apoptosis, and its function and activity can be modulated by cellular redistribution. Green fluorescent protein-tagged Nur77 was used to evaluate the role of Nur77 intracellular redistribution in response to genotoxic stress. Selected DNA damaging agents and transcription inhibition lead to rapid redistribution of Nur77 into nuclear structures distinct from conventional nuclear bodies. These nuclear bodies formed transiently were tightly bound to the nuclear matrix and conditions that lead to their appearance were associated with Nur77 transcriptional inhibition. The formation of Nur77 nuclear bodies might be involved in programmed cell death modulation upon exposure to DNA damaging agents that inhibit transcription by sequestrating this proapoptotic factor in dense nuclear structures

  5. Early diagnostics of temporomandibular joint structural elements injures caused by traumatic mandibular bone fractures.

    Science.gov (United States)

    Pohranychna, Kh R; Stasyshyn, A R; Matolych, U D

    2017-06-30

    A rapidly increasing number of mandibular condylar fractures and some complications related to injuries of temporomandibular elements make this study important. Intra-articular disorders lead to secondary pathological findings such as osteoarthritis, deforming osteoarthrosis, and temporomandibular joint ankylosis that limits mouth opening, mastication, swallowing, breathing, and decreased/lost working capacity or disability. Early diagnosis of intra-articular disorders can prevent from long-lasting functional complications caused by temporomandibular joint injuries. This study was performed for the purpose of early detection and investigation of organic pathological changes in the cartilaginous and osseous tissues of the temporomandibular joint caused by traumatic fractures of the mandibular condyle. Twenty patients underwent a general clinical examination, magnetic resonance imaging (MRI), and immune-enzyme testing for biochemical markers of connective tissue injury (pyridinoline and deoxypyridinoline) in urine. Disk dislocation, deformation, adhesion, perforation or squeeze, tension or disruption of ligaments, and injury of articular surfaces are among complications of mandibular fractures that can be revealed on MRI. As regards biochemical findings, we revealed a sharp rise in the levels of pyridinoline and deoxypyridinoline before treatment and a lack of stabilization within 21 days of treatment.

  6. Portfolio Sensitivity Model for Analyzing Credit Risk Caused by Structural and Macroeconomic Changes

    Directory of Open Access Journals (Sweden)

    Goran Klepac

    2008-12-01

    Full Text Available This paper proposes a new model for portfolio sensitivity analysis. The model is suitable for decision support in financial institutions, specifically for portfolio planning and portfolio management. The basic advantage of the model is the ability to create simulations for credit risk predictions in cases when we virtually change portfolio structure and/or macroeconomic factors. The model takes a holistic approach to portfolio management consolidating all organizational segments in the process such as marketing, retail and risk.

  7. How the ownership structures cause epidemics in financial markets: A network-based simulation model

    Science.gov (United States)

    Dastkhan, Hossein; Gharneh, Naser Shams

    2018-02-01

    Analysis of systemic risks and contagions is one of the main challenges of policy makers and researchers in the recent years. Network theory is introduced as a main approach in the modeling and simulation of financial and economic systems. In this paper, a simulation model is introduced based on the ownership network to analyze the contagion and systemic risk events. For this purpose, different network structures with different values for parameters are considered to investigate the stability of the financial system in the presence of different kinds of idiosyncratic and aggregate shocks. The considered network structures include Erdos-Renyi, core-periphery, segregated and power-law networks. Moreover, the results of the proposed model are also calculated for a real ownership network. The results show that the network structure has a significant effect on the probability and the extent of contagion in the financial systems. For each network structure, various values for the parameters results in remarkable differences in the systemic risk measures. The results of real case show that the proposed model is appropriate in the analysis of systemic risk and contagion in financial markets, identification of systemically important firms and estimation of market loss when the initial failures occur. This paper suggests a new direction in the modeling of contagion in the financial markets, in particular that the effects of new kinds of financial exposure are clarified. This paper's idea and analytical results may also be useful for the financial policy makers, portfolio managers and the firms to conduct their investment in the right direction.

  8. 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 formati...

  9. Structure in defocused beams of x-ray mirrors: causes and possible solutions

    Science.gov (United States)

    Sutter, John P.; Alcock, Simon G.; Rust, Fiona; Wang, Hongchang; Sawhney, Kawal

    2014-09-01

    Grazing incidence mirrors are now a standard optic for focusing X-ray beams. Both bimorph and mechanically bendable mirrors are widely used at Diamond Light Source because they permit a wide choice of focal lengths. They can also be deliberately set out of focus to enlarge the X-ray beam, and indeed many beamline teams now wish to generate uniform beam spots of variable size. However, progress has been slowed by the appearance of fine structure in these defocused beams. Measurements showing the relationship between the medium-frequency polishing error and this structure over a variety of beam sizes will be presented. A theoretical model for the simulations of defocused beams from general mirrors will then be developed. Not only the figure error and its first derivative the slope error, but also the second derivative, the curvature error, must be considered. In conclusion, possible ways to reduce the defocused beam structure by varying the actuators' configuration and settings will be discussed.

  10. Testing the gravitational instability hypothesis?

    Science.gov (United States)

    Babul, Arif; Weinberg, David H.; Dekel, Avishai; Ostriker, Jeremiah P.

    1994-01-01

    We challenge a widely accepted assumption of observational cosmology: that successful reconstruction of observed galaxy density fields from measured galaxy velocity fields (or vice versa), using the methods of gravitational instability theory, implies that the observed large-scale structures and large-scale flows were produced by the action of gravity. This assumption is false, in that there exist nongravitational theories that pass the reconstruction tests and gravitational theories with certain forms of biased galaxy formation that fail them. Gravitational instability theory predicts specific correlations between large-scale velocity and mass density fields, but the same correlations arise in any model where (a) structures in the galaxy distribution grow from homogeneous initial conditions in a way that satisfies the continuity equation, and (b) the present-day velocity field is irrotational and proportional to the time-averaged velocity field. We demonstrate these assertions using analytical arguments and N-body simulations. If large-scale structure is formed by gravitational instability, then the ratio of the galaxy density contrast to the divergence of the velocity field yields an estimate of the density parameter Omega (or, more generally, an estimate of beta identically equal to Omega(exp 0.6)/b, where b is an assumed constant of proportionality between galaxy and mass density fluctuations. In nongravitational scenarios, the values of Omega or beta estimated in this way may fail to represent the true cosmological values. However, even if nongravitational forces initiate and shape the growth of structure, gravitationally induced accelerations can dominate the velocity field at late times, long after the action of any nongravitational impulses. The estimated beta approaches the true value in such cases, and in our numerical simulations the estimated beta values are reasonably accurate for both gravitational and nongravitational models. Reconstruction tests

  11. 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.

  12. Instabilities in the plasma focus

    International Nuclear Information System (INIS)

    Kaeppeler, H.J.

    1975-03-01

    The plasma focus was studied by many research teams in view of a possible approach to controlled thermonuclear fusion. Though it is questionable whether the plasma focus will ever lead to a fusion reactor, it nevertheless constitutes a strong source of neutron, X- and gamma radiation for simulating fusion reactor conditions. Furthermore, the plasma focus yields very high temperatures (10 7 K) and densities (> 10 19 cm -3 ) and thus provides interesting conditions for the study of high density plasmas. This review paper starts with a description of the compression stage of the focussing plasma, using a snow-plough model. It is shown that sophisticated MHD calculations substantiate the snowplough theory, but are not suited to describe the phenomena in the final compressed stage. For this purpose, a particle-in-cell calculation is employed, yielding a beam-beam collision model for the neutron production. Experimental evidence indicates that neutron production is associated with the appearence of m = O instabilities and is the direct result of collisions between anomalously accelerated ions. One of the mechanisms of ion acceleration are strong local electric fields. Another possible mechanism can bee seen in beam-plasma instabilities caused by runaway electrons. The analytical derivation of the dispersion relation for plasma focus conditions including runaway effect is discussed (orig.) [de

  13. Tracking Code for Microwave Instability

    International Nuclear Information System (INIS)

    Heifets, S.; SLAC

    2006-01-01

    To study microwave instability the tracking code is developed. For bench marking, results are compared with Oide-Yokoya results [1] for broad-band Q = 1 impedance. Results hint to two possible mechanisms determining the threshold of instability

  14. Instabilities in thin tunnel junctions

    International Nuclear Information System (INIS)

    Konkin, M.K.; Adler, J.G.

    1978-01-01

    Tunnel junctions prepared for inelastic electron tunneling spectroscopy are often plagued by instabilities in the 0-500-meV range. This paper relates the bias at which the instability occurs to the barrier thickness

  15. Numerical study of the effect of inlet geometry on combustion instabilities in a lean premixed swirl combustor

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chang Eon [Dept. of Mechanical Engineering, Inha University, Incheon (Korea, Republic of); Park, Seul Hyun [Dept. of Mechanical Systems Engineering, Chosun University, Gwangju (Korea, Republic of); Hwang, Cheol Hong [Dept. of Fire and Disaster Prevention, Daejeon University, Daejeon (Korea, Republic of)

    2016-11-15

    The effects of flow structure and flame dynamics on combustion instabilities in a lean premixed swirl combustor were numerically investigated using Large eddy simulation (LES) by varying the inlet geometry of combustor. The dynamic ksgs-equation and G-equation flamelet models were respectively employed as the LES subgrid models of turbulence and combustion. The divergent half angle (α) in the combustor inlet was varied systematically from 30° to 90° to quantify the effect of inlet geometry on the combustion instabilities. This variation caused considerable deformation in recirculation zones in terms of their size and location, leading to significant changes in flame dynamics. Analysis of unsteady pressure distributions in the combustor showed that the largest damping caused by combustion instabilities takes place at α = 45°, and the amplitude of acoustic pressure oscillation is largest at α = 30°. Examination of local Rayleigh parameters indicated that controlling flame-vortex interactions by modifying inlet geometry can change the local characteristics of combustion instabilities in terms of their amplification and suppression, and thus serve as a useful approach to reduce the instabilities in a lean premixed swirl combustor. These phenomena were studied in detail through unsteady analysis associated with flow and flame dynamics.

  16. Numerical study of the effect of inlet geometry on combustion instabilities in a lean premixed swirl combustor

    International Nuclear Information System (INIS)

    Lee, Chang Eon; Park, Seul Hyun; Hwang, Cheol Hong

    2016-01-01

    The effects of flow structure and flame dynamics on combustion instabilities in a lean premixed swirl combustor were numerically investigated using Large eddy simulation (LES) by varying the inlet geometry of combustor. The dynamic ksgs-equation and G-equation flamelet models were respectively employed as the LES subgrid models of turbulence and combustion. The divergent half angle (α) in the combustor inlet was varied systematically from 30° to 90° to quantify the effect of inlet geometry on the combustion instabilities. This variation caused considerable deformation in recirculation zones in terms of their size and location, leading to significant changes in flame dynamics. Analysis of unsteady pressure distributions in the combustor showed that the largest damping caused by combustion instabilities takes place at α = 45°, and the amplitude of acoustic pressure oscillation is largest at α = 30°. Examination of local Rayleigh parameters indicated that controlling flame-vortex interactions by modifying inlet geometry can change the local characteristics of combustion instabilities in terms of their amplification and suppression, and thus serve as a useful approach to reduce the instabilities in a lean premixed swirl combustor. These phenomena were studied in detail through unsteady analysis associated with flow and flame dynamics

  17. Structurally diverse natural products that cause potassium leakage trigger multicellularity in Bacillus subtilis.

    Science.gov (United States)

    López, Daniel; Fischbach, Michael A; Chu, Frances; Losick, Richard; Kolter, Roberto

    2009-01-06

    We report a previously undescribed quorum-sensing mechanism for triggering multicellularity in Bacillus subtilis. B. subtilis forms communities of cells known as biofilms in response to an unknown signal. We discovered that biofilm formation is stimulated by a variety of small molecules produced by bacteria--including the B. subtilis nonribosomal peptide surfactin--that share the ability to induce potassium leakage. Natural products that do not cause potassium leakage failed to induce multicellularity. Small-molecule-induced multicellularity was prevented by the addition of potassium, but not sodium or lithium. Evidence is presented that potassium leakage stimulates the activity of a membrane protein kinase, KinC, which governs the expression of genes involved in biofilm formation. We propose that KinC responds to lowered intracellular potassium concentration and that this is a quorum-sensing mechanism that enables B. subtilis to respond to related and unrelated bacteria.

  18. Topographic precursors and geological structures of deep-seated catastrophic landslides caused by Typhoon Talas

    Science.gov (United States)

    Chigira, Masahiro; Tsou, Ching-Ying; Matsushi, Yuki; Hiraishi, Narumi; Matsuzawa, Makoto

    2013-11-01

    Typhoon Talas crossed the Japanese Islands between 2 and 5 September 2011, causing more than 70 deep-seated catastrophic landslides in a Jurassic to Paleogene-lower Miocene accretion complex. Detailed examination of the topographic features of 10 large landslides before the event, recorded on 1-m DEMs based on airborne laser scanner surveys, showed that all landslides had small scarps near their future crowns prior to the slide, and one landslide had linear depressions along its future crown as precursor topographic features. These scarps and linear depressions were caused by gravitational slope deformation that preceded the catastrophic failure. Although the scarps may have been enlarged by degradation, their sizes relative to the whole slopes suggest that minimal slope deformation had occurred in the period immediately before the catastrophic failure. The scarp ratio, defined as the ratio of length of a scarp to that of the whole slope both measured along the slope line, ranged from 5% to 21%. Careful examination of aerial photographs from another four large landslides, for which no high-resolution DEMs were available, suggested that they also developed scarps at their heads beforehand. Twelve of the 14 landslides we surveyed in the field had sliding surfaces with wedge-shaped discontinuities that consisted of faults and bedding, suggesting that the buildup of pore pressure occurs readily on wedge-shaped discontinuities in a gravitationally deformed rock body. Most of the faults were undulatory and were probably thrust faults that formed during accretion. Other types of gravitational deformation were also active; e.g., flexural toppling and buckling were observed to have preceded one landslide.

  19. Guidelines for Safety Evaluation of a Potential for PWR Steam Generator Tube Failure due to Fluid elastic Instability

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Jong Chull; Do, Kyu Sik; Sheen, Cheol [Nuclear System Evaluation Dept., Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of)

    2013-05-15

    It was found that both SG tube rupture events occurred at North Anna Unit 1 in 1987 and at Mihama Unit 2 in 1991 were caused by a high cycle fatigue due to fluid elastic instability. Therefore, with regard to nuclear safety it is important to design the SG properly in a conservative manner so that the potential for SG U-tube failures due to fluid elastic instability can be minimized. This article provides guidelines for assessing the potential for SG U-tube damage due to fluid elastic instability. This article described guidelines for safety evaluation of a potential for PWR steam generator tube failure due to fluid elastic instability. The guidelines address the requirements for realistically performing the SG thermal-hydraulic analysis and the modal analysis of tubes as well as the criteria for conservatively determining the added mass, the damping ratio and the fluid elastic instability coefficient. The guidelines can be used to predict the potential SG tubes which are susceptible to failure due to fluid elastic instability at operating nuclear power plants and also to evaluate the safety and structural integrity of new SG designs at the licensing review stage. Failure of a pressurized water reactor (PWR) steam generator (SG) tube leads to a leakage of contaminated primary coolant to the secondary system, which has serious safety implications such as the potential for direct release of radioactive fission products to the environment and the loss of coolant. Excessive tube vibration excited by dynamic forces of internal or external fluid flow is called flow-induced vibration (FIV). Among the FIV mechanisms, the so-called fluid elastic instability of SG tubes in cross flow is the most important safety issue in the design of SGs because it may cause severe tube failure in a very short time.

  20. Nonlinear evolution of MHD instabilities

    International Nuclear Information System (INIS)

    Bateman, G.; Hicks, H.R.; Wooten, J.W.; Dory, R.A.

    1975-01-01

    A 3-D nonlinear MHD computer code was used to study the time evolution of internal instabilities. Velocity vortex cells are observed to persist into the nonlinear evolution. Pressure and density profiles convect around these cells for a weak localized instability, or convect into the wall for a strong instability. (U.S.)

  1. PSO (Particle Swarm Optimization) for Interpretation of Magnetic Anomalies Caused by Simple Geometrical Structures

    Science.gov (United States)

    Essa, Khalid S.; Elhussein, Mahmoud

    2018-04-01

    A new efficient approach to estimate parameters that controlled the source dimensions from magnetic anomaly profile data in light of PSO algorithm (particle swarm optimization) has been presented. The PSO algorithm has been connected in interpreting the magnetic anomaly profiles data onto a new formula for isolated sources embedded in the subsurface. The model parameters deciphered here are the depth of the body, the amplitude coefficient, the angle of effective magnetization, the shape factor and the horizontal coordinates of the source. The model parameters evaluated by the present technique, generally the depth of the covered structures were observed to be in astounding concurrence with the real parameters. The root mean square (RMS) error is considered as a criterion in estimating the misfit between the observed and computed anomalies. Inversion of noise-free synthetic data, noisy synthetic data which contains different levels of random noise (5, 10, 15 and 20%) as well as multiple structures and in additional two real-field data from USA and Egypt exhibits the viability of the approach. Thus, the final results of the different parameters are matched with those given in the published literature and from geologic results.

  2. Structure and dimensions of radioactive contamination caused by use of nuclear weapons

    International Nuclear Information System (INIS)

    Ilijas, B.

    1996-01-01

    Radioactive contamination is one of unavoidable consequences of nuclear burst. Its structure and dimensions are depended of many factors connected with type of weapon, with meteorological conditions and location of burst and characteristics of area involved. Contamination manifests in two ways - as induced radioactivity in the nearness of the center of explosion and as radioactive fallout. Induced radioactivity originates from interaction of neutrons from primary beam with elements naturally presents in environment, which results in creating radionuclides and area of radioactive contamination. Radioactive fallout consists of material formed or collected in the explosion that falls on earth in form of small particles. This contaminant contains α, β and γ sources with structure dependent of explosive energy and location of burst. Some radionuclides, often present in fallout, are very dangerous as internal sources ( 90 Sr, 131 I, 137 Cs, 239 Pu). Dimension of contaminated area varies widely, but if one has Knowledge of enough parameters, it is possible to predict its shape, as well as dose rate on some distance from zero point. Preciseness of this work is essentially affected by credibility of data involved and by kind of selected model. Using of well-chosen model enables on-time evaluation of risk from radioactive contamination and planning adequate protection. (author)

  3. Compensatory mutations cause excess of antagonistic epistasis in RNA secondary structure folding

    Directory of Open Access Journals (Sweden)

    Adami Christoph

    2003-02-01

    Full Text Available Background The rate at which fitness declines as an organism's genome accumulates random mutations is an important variable in several evolutionary theories. At an intuitive level, it might seem natural that random mutations should tend to interact synergistically, such that the rate of mean fitness decline accelerates as the number of random mutations is increased. However, in a number of recent studies, a prevalence of antagonistic epistasis (the tendency of multiple mutations to have a mitigating rather than reinforcing effect has been observed. Results We studied in silico the net amount and form of epistatic interactions in RNA secondary structure folding by measuring the fraction of neutral mutants as a function of mutational distance d. We found a clear prevalence of antagonistic epistasis in RNA secondary structure folding. By relating the fraction of neutral mutants at distance d to the average neutrality at distance d, we showed that this prevalence derives from the existence of many compensatory mutations at larger mutational distances. Conclusions Our findings imply that the average direction of epistasis in simple fitness landscapes is directly related to the density with which fitness peaks are distributed in these landscapes.

  4. Compensatory mutations cause excess of antagonistic epistasis in RNA secondary structure folding.

    Science.gov (United States)

    Wilke, Claus O; Lenski, Richard E; Adami, Christoph

    2003-02-05

    The rate at which fitness declines as an organism's genome accumulates random mutations is an important variable in several evolutionary theories. At an intuitive level, it might seem natural that random mutations should tend to interact synergistically, such that the rate of mean fitness decline accelerates as the number of random mutations is increased. However, in a number of recent studies, a prevalence of antagonistic epistasis (the tendency of multiple mutations to have a mitigating rather than reinforcing effect) has been observed. We studied in silico the net amount and form of epistatic interactions in RNA secondary structure folding by measuring the fraction of neutral mutants as a function of mutational distance d. We found a clear prevalence of antagonistic epistasis in RNA secondary structure folding. By relating the fraction of neutral mutants at distance d to the average neutrality at distance d, we showed that this prevalence derives from the existence of many compensatory mutations at larger mutational distances. Our findings imply that the average direction of epistasis in simple fitness landscapes is directly related to the density with which fitness peaks are distributed in these landscapes.

  5. Mirror Instability in the Turbulent Solar Wind

    Energy Technology Data Exchange (ETDEWEB)

    Hellinger, Petr [Astronomical Institute, CAS, Bocni II/1401,CZ-14100 Prague (Czech Republic); Landi, Simone; Verdini, Andrea; Franci, Luca [Dipartimento di Fisica e Astronomia, Università degli Studi di Firenze Largo E. Fermi 2, I-50125 Firenze (Italy); Matteini, Lorenzo, E-mail: petr.hellinger@asu.cas.cz [Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)

    2017-04-01

    The relationship between a decaying strong turbulence and the mirror instability in a slowly expanding plasma is investigated using two-dimensional hybrid expanding box simulations. We impose an initial ambient magnetic field perpendicular to the simulation box, and we start with a spectrum of large-scale, linearly polarized, random-phase Alfvénic fluctuations that have energy equipartition between kinetic and magnetic fluctuations and a vanishing correlation between the two fields. A turbulent cascade rapidly develops, magnetic field fluctuations exhibit a Kolmogorov-like power-law spectrum at large scales and a steeper spectrum at sub-ion scales. The imposed expansion (taking a strictly transverse ambient magnetic field) leads to the generation of an important perpendicular proton temperature anisotropy that eventually drives the mirror instability. This instability generates large-amplitude, nonpropagating, compressible, pressure-balanced magnetic structures in a form of magnetic enhancements/humps that reduce the perpendicular temperature anisotropy.

  6. Dynamics and Instabilities of Vortex Pairs

    Science.gov (United States)

    Leweke, Thomas; Le Dizès, Stéphane; Williamson, Charles H. K.

    2016-01-01

    This article reviews the characteristics and behavior of counter-rotating and corotating vortex pairs, which are seemingly simple flow configurations yet immensely rich in phenomena. Since the reviews in this journal by Widnall (1975) and Spalart (1998) , who studied the fundamental structure and dynamics of vortices and airplane trailing vortices, respectively, there have been many analytical, computational, and experimental studies of vortex pair flows. We discuss two-dimensional dynamics, including the merging of same-sign vortices and the interaction with the mutually induced strain, as well as three-dimensional displacement and core instabilities resulting from this interaction. Flows subject to combined instabilities are also considered, in particular the impingement of opposite-sign vortices on a ground plane. We emphasize the physical mechanisms responsible for the flow phenomena and clearly present the key results that are useful to the reader for predicting the dynamics and instabilities of parallel vortices.

  7. Thermal instability in a stratified plasma

    International Nuclear Information System (INIS)

    Hermanns, D.F.M.; Priest, E.R.

    1989-01-01

    The thermal instability mechansism has been studied in connection to observed coronal features, like, e.g. prominences or cool cores in loops. Although these features show a lot of structure, most studies concern the thermal instability in an uniform medium. In this paper, we investigate the thermal instability and the interaction between thermal modes and the slow magneto-acoustic subspectrum for a stratified plasma slab. We fomulate the relevant system of equations and give some straightforward properties of the linear spectrum of a non-uniform plasma slab, i.e. the existence of continuous parts in the spectrum. We present a numerical scheme with which we can investigate the linear spectrum for equilibrium states with stratification. The slow and thermal subspectra of a crude coronal model are given as a preliminary result. (author). 6 refs.; 1 fig

  8. Progressive alterations of central nervous system structure and function are caused by charged particle radiation

    Science.gov (United States)

    Nelson, G. A.; Cns Nscor Team

    A new NASA-sponsored program project (NSCOR) has been organized to conduct the first comprehensive investigation of the response of a mammalian brain structure (mouse hippocampus) to charged-particle radiation. The NSCOR collaboration has three main goals. The first goal is to quantify the time- and dose-dependent changes in cellular composition and architecture. By using stereology on preserved brains, subsets of cells (neurons, glia, endothelia and stem cells) will be quantified out to 2 years after irradiation with accelerated protons and iron ions. To further characterize changes in vasculature architecture a polymer infusion technique will be used to produce a three-dimensional vasculature cast that then will be mapped by x-ray tomography to determine topological changes, and microscopic infarcts associated with amyloid protein deposits. The 2nd goal is to quantify hippocampal function(s). The primary measurement of function will be extracellular electrical recordings from hippocampal ``brain slices'' that reflect underlying functions such as connectivity, action potential generation & conduction, and neurotransmitter formation, secretion, and uptake. Individual nerve membrane properties will be assessed by ``patch clamp'' recordings. Two non-invasive methods will evaluate brain function and the evolution of changes with time. Electroencephalograms will map macroscopic spontaneous electrical activity while two state-of-the-art MRI magnetization sequences will visualize and quantify local oxygen utilization and white matter fiber tracts structural integrity. To quantify the brains' overall performance under stress, animals will receive a systemic shock mediated by the immune system in the form of a reaction to lipopolysaccharide. A second strategy will employ the APP23 transgenic mouse that develops the pathological changes associated with Alzheimer's disease. Measurements of irradiated mice will determine whether radiation exposure affects the latency and

  9. The human factor as a cause of failures in building structures

    Directory of Open Access Journals (Sweden)

    Vondráčková Terezie

    2017-01-01

    Full Text Available Human error can be defined as any unintentional or inadequate decision, taken at any level in the hierarchy of an organization, which is, or was inappropriate in a given situation. Human errors can occur in all human activities across an organization - at a managerial, conceptual or technical level – in connection with mistakes in the construction project itself, mistakes made by the investor, mistakes made by those using the building, mistakes in supplier relations, mistakes in the maintenance of the structure, and others. The factors that can affect the reliability of those people making the decisions that lead to the mistakes include the quality of their education, their experience with stress, or lack thereof, as well as issues such as workload, fatigue, workplace ergonomics, working hours, social climate and private matters.

  10. Matlab fractal techniques used to study the structural degradation caused by alpha radiation to laser mirrors

    Science.gov (United States)

    Ioan, M.-R.

    2018-01-01

    Almost all optical diagnostic systems associated with classical particle accelerators or with new state-of-the-art particle accelerators, such as those developed within the European Collaboration ELI-NP (Extreme Light Infrastructure-Nuclear Physics) (involving extreme power laser beams), contain in their infrastructure high quality laser mirrors, used for their reflectivity and/or their partial transmittance. These high quality mirrors facilitate the extraction and handling of optical signals. When optical mirrors are exposed to high energy ionizing radiation fields, their optical and structural properties will change over time and their functionality will be affected, meaning that they will provide imprecise information. In some experiments, being exposed to mixed laser and accelerated particle beams, the deterioration of laser mirrors is even more acute, since the destruction mechanisms of both types of beams are cumulated. The main task of the work described in this paper was to find a novel specific method to analyse and highlight such degradation processes. By using complex fractal techniques integrated in a MATLAB code, the effects induced by alpha radiation to laser mirrors were studied. The fractal analysis technique represents an alternative approach to the classical Euclidean one. It can be applied for the characterization of the defects occurred in mirrors structure due to their exposure to high energy alpha particle beams. The proposed method may be further integrated into mirrors manufacturing process, as a testing instrument, to obtain better quality mirrors (enhanced resistance to high energy ionizing beams) by using different types of reflective coating materials and different deposition techniques. Moreover, the effect of high energy alpha ionizing particles on the optical properties of the exposed laser mirrors was studied by using spectrophotometric techniques.

  11. Can tokamaks PFC survive a single event of any plasma instabilities?

    Energy Technology Data Exchange (ETDEWEB)

    Hassanein, A., E-mail: hassanein@purdue.edu [Center for Materials under Extreme Environment, School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907 (United States); Sizyuk, V.; Miloshevsky, G.; Sizyuk, T. [Center for Materials under Extreme Environment, School of Nuclear Engineering, Purdue University, 400 Central Drive, West Lafayette, IN 47907 (United States)

    2013-07-15

    Plasma instability events such as disruptions, edge-localized modes (ELMs), runaway electrons (REs), and vertical displacement events (VDEs) are continued to be serious events and most limiting factors for successful tokamak reactor concept. The plasma-facing components (PFCs), e.g., wall, divertor, and limited surfaces of a tokamak as well as coolant structure materials are subjected to intense particle and heat loads and must maintain a clean and stable surface environment among them and the core/edge plasma. Typical ITER transient events parameters are used for assessing the damage from these four different instability events. HEIGHTS simulation showed that a single event of a disruption, giant ELM, VDE, or RE can cause significant surface erosion (melting and vaporization) damage to PFC, nearby components, and/or structural materials (VDE, RE) melting and possible burnout of coolant tubes that could result in shut down of reactor for extended repair time.

  12. Can tokamaks PFC survive a single event of any plasma instabilities?

    Science.gov (United States)

    Hassanein, A.; Sizyuk, V.; Miloshevsky, G.; Sizyuk, T.

    2013-07-01

    Plasma instability events such as disruptions, edge-localized modes (ELMs), runaway electrons (REs), and vertical displacement events (VDEs) are continued to be serious events and most limiting factors for successful tokamak reactor concept. The plasma-facing components (PFCs), e.g., wall, divertor, and limited surfaces of a tokamak as well as coolant structure materials are subjected to intense particle and heat loads and must maintain a clean and stable surface environment among them and the core/edge plasma. Typical ITER transient events parameters are used for assessing the damage from these four different instability events. HEIGHTS simulation showed that a single event of a disruption, giant ELM, VDE, or RE can cause significant surface erosion (melting and vaporization) damage to PFC, nearby components, and/or structural materials (VDE, RE) melting and possible burnout of coolant tubes that could result in shut down of reactor for extended repair time.

  13. Can tokamaks PFC survive a single event of any plasma instabilities?

    International Nuclear Information System (INIS)

    Hassanein, A.; Sizyuk, V.; Miloshevsky, G.; Sizyuk, T.

    2013-01-01

    Plasma instability events such as disruptions, edge-localized modes (ELMs), runaway electrons (REs), and vertical displacement events (VDEs) are continued to be serious events and most limiting factors for successful tokamak reactor concept. The plasma-facing components (PFCs), e.g., wall, divertor, and limited surfaces of a tokamak as well as coolant structure materials are subjected to intense particle and heat loads and must maintain a clean and stable surface environment among them and the core/edge plasma. Typical ITER transient events parameters are used for assessing the damage from these four different instability events. HEIGHTS simulation showed that a single event of a disruption, giant ELM, VDE, or RE can cause significant surface erosion (melting and vaporization) damage to PFC, nearby components, and/or structural materials (VDE, RE) melting and possible burnout of coolant tubes that could result in shut down of reactor for extended repair time

  14. 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.

  15. Adhesional instabilities and gecko locomotion

    International Nuclear Information System (INIS)

    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. (paper)

  16. Instabilities in strongly coupled plasmas

    CERN Document Server

    Kalman, G J

    2003-01-01

    The conventional Vlasov treatment of beam-plasma instabilities is inappropriate when the plasma is strongly coupled. In the strongly coupled liquid state, the strong correlations between the dust grains fundamentally affect the conditions for instability. In the crystalline state, the inherent anisotropy couples the longitudinal and transverse polarizations, and results in unstable excitations in both polarizations. We summarize analyses of resonant and non-resonant, as well as resistive instabilities. We consider both ion-dust streaming and dust beam-plasma instabilities. Strong coupling, in general, leads to an enhancement of the growth rates. In the crystalline phase, a resonant transverse instability can be excited.

  17. A trickle instability

    Science.gov (United States)

    Bossa, Benjamin

    2005-11-01

    We address the problem of the free fall of a long, horizontal and narrow liquid layer squeezed in a vertical open Hele-Shaw cell. The layer destabilizes as it falls down, evolving into a series of liquid blobs linked together by thin bridges, which ultimately break, leaving the initially connex fluid layer as a set a disjointed drops. The mechanism of this instability is the onset of a vertical pressure gradient due to the curvature difference of the moving contact line between the advancing interface and the rear interface. This instability, whose growth rate scales with a non-trivial power of the capillary number, amplifies indifferently a broad band of wavenumbers because of the flat shape of its dispersion relation in the thin layer limit. We will finally comment on the nature of the final fragmentation process and drop size distributions.

  18. 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.

  19. Linear waves and instabilities

    International Nuclear Information System (INIS)

    Bers, A.

    1975-01-01

    The electrodynamic equations for small-amplitude waves and their dispersion relation in a homogeneous plasma are outlined. For such waves, energy and momentum, and their flow and transformation, are described. Perturbation theory of waves is treated and applied to linear coupling of waves, and the resulting instabilities from such interactions between active and passive waves. Linear stability analysis in time and space is described where the time-asymptotic, time-space Green's function for an arbitrary dispersion relation is developed. The perturbation theory of waves is applied to nonlinear coupling, with particular emphasis on pump-driven interactions of waves. Details of the time--space evolution of instabilities due to coupling are given. (U.S.)

  20. Cosmic ray driven instability

    International Nuclear Information System (INIS)

    Dorfi, E.A.; Drury, L.O.

    1985-01-01

    The interaction between energetic charged particles and thermal plasma, which forms the basis of diffusive shock acceleration, leads also to interesting dynamical phenomena. For a compressional mode propagating in a system with homoeneous energetic particle pressure it is well known that friction with the energetic particles leads to damping. The linear theory of this effect has been analyzed in detail by Ptuskin. Not so obvious is that a non-uniform energetic particle pressure can in addition amplify compressional disturbances. If the pressure gradient is sufficiently steep this growth can dominate the frictional damping and lead to an instability. It is important to not that this effect results from the collective nature of the interaction between the energetic particles and the gas and is not connected with the Parker instability, nor with the resonant amplification of Alfven waves

  1. Mucin deficiency causes functional and structural changes of the ocular surface.

    Science.gov (United States)

    Floyd, Anne M; Zhou, Xu; Evans, Christopher; Rompala, Olivia J; Zhu, Lingxiang; Wang, Mingwu; Chen, Yin

    2012-01-01

    MUC5AC is the most abundant gel-forming mucin in the ocular system. However, the specific function is unknown. In the present study, a Muc5ac knockout (KO) mouse model was subject to various physiological measurements as compared to its wide-type (WT) control. Interestingly, when KO mice were compared to WT mice, the mean tear break up time (TBUT) values were significantly lower and corneal fluorescein staining scores were significantly higher. But the tear volume was not changed. Despite the lack of Muc5ac expression in the conjunctiva of KO mice, Muc5b expression was significantly increased in these mice. Corneal opacification, varying in location and severity, was found in a few KO mice but not in WT mice. The present results suggest a significant difference in the quality, but not the quantity, of tear fluid in the KO mice compared to WT mice. Dry eye disease is multifactorial and therefore further evaluation of the varying components of the tear film, lacrimal unit and corneal structure of these KO mice may help elucidate the role of mucins in dry eye disease. Because Muc5ac knockout mice have clinical features of dry eye, this mouse model will be extremely useful for further studies regarding the pathophysiology of the ocular surface in dry eye in humans.

  2. Mucin deficiency causes functional and structural changes of the ocular surface.

    Directory of Open Access Journals (Sweden)

    Anne M Floyd

    Full Text Available MUC5AC is the most abundant gel-forming mucin in the ocular system. However, the specific function is unknown. In the present study, a Muc5ac knockout (KO mouse model was subject to various physiological measurements as compared to its wide-type (WT control. Interestingly, when KO mice were compared to WT mice, the mean tear break up time (TBUT values were significantly lower and corneal fluorescein staining scores were significantly higher. But the tear volume was not changed. Despite the lack of Muc5ac expression in the conjunctiva of KO mice, Muc5b expression was significantly increased in these mice. Corneal opacification, varying in location and severity, was found in a few KO mice but not in WT mice. The present results suggest a significant difference in the quality, but not the quantity, of tear fluid in the KO mice compared to WT mice. Dry eye disease is multifactorial and therefore further evaluation of the varying components of the tear film, lacrimal unit and corneal structure of these KO mice may help elucidate the role of mucins in dry eye disease. Because Muc5ac knockout mice have clinical features of dry eye, this mouse model will be extremely useful for further studies regarding the pathophysiology of the ocular surface in dry eye in humans.

  3. The Selfish Goal: autonomously operating motivational structures as the proximate cause of human judgment and behavior.

    Science.gov (United States)

    Huang, Julie Y; Bargh, John A

    2014-04-01

    We propose the Selfish Goal model, which holds that a person's behavior is driven by psychological processes called goals that guide his or her behavior, at times in contradictory directions. Goals can operate both consciously and unconsciously, and when activated they can trigger downstream effects on a person's information processing and behavioral possibilities that promote only the attainment of goal end-states (and not necessarily the overall interests of the individual). Hence, goals influence a person as if the goals themselves were selfish and interested only in their own completion. We argue that there is an evolutionary basis to believe that conscious goals evolved from unconscious and selfish forms of pursuit. This theoretical framework predicts the existence of unconscious goal processes capable of guiding behavior in the absence of conscious awareness and control (the automaticity principle), the ability of the most motivating or active goal to constrain a person's information processing and behavior toward successful completion of that goal (the reconfiguration principle), structural similarities between conscious and unconscious goal pursuit (the similarity principle), and goal influences that produce apparent inconsistencies or counterintuitive behaviors in a person's behavior extended over time (the inconsistency principle). Thus, we argue that a person's behaviors are indirectly selected at the goal level but expressed (and comprehended) at the individual level.

  4. Instability in dynamic fracture

    Science.gov (United States)

    Fineberg, J.; Marder, M.

    1999-05-01

    The fracture of brittle amorphous materials is an especially challenging problem, because the way a large object shatters is intimately tied to details of cohesion at microscopic scales. This subject has been plagued by conceptual puzzles, and to make matters worse, experiments seemed to contradict the most firmly established theories. In this review, we will show that the theory and experiments fit within a coherent picture where dynamic instabilities of a crack tip play a crucial role. To accomplish this task, we first summarize the central results of linear elastic dynamic fracture mechanics, an elegant and powerful description of crack motion from the continuum perspective. We point out that this theory is unable to make predictions without additional input, information that must come either from experiment, or from other types of theories. We then proceed to discuss some of the most important experimental observations, and the methods that were used to obtain the them. Once the flux of energy to a crack tip passes a critical value, the crack becomes unstable, and it propagates in increasingly complicated ways. As a result, the crack cannot travel as quickly as theory had supposed, fracture surfaces become rough, it begins to branch and radiate sound, and the energy cost for crack motion increases considerably. All these phenomena are perfectly consistent with the continuum theory, but are not described by it. Therefore, we close the review with an account of theoretical and numerical work that attempts to explain the instabilities. Currently, the experimental understanding of crack tip instabilities in brittle amorphous materials is fairly detailed. We also have a detailed theoretical understanding of crack tip instabilities in crystals, reproducing qualitatively many features of the experiments, while numerical work is beginning to make the missing connections between experiment and theory.

  5. Thresholds of a bunched beam longitudinal instability in proton synchrotrons

    International Nuclear Information System (INIS)

    Balbekov, V.I.; Ivanov, S.V.

    1986-01-01

    The formulas and graphs for calculating instability thresholds arising during the interaction of a bunched proton beam with narrow-band resonator are given. The instabilities of three types with oscillations of a definite multipolarity, oscillations of some bound multipoles and with microwave oscillations arising as a result of addition of a great number of multipoles. The analysis of the above data shows that the increase of oscillations nonlinearity is accompanied by the growth of instability threshold only in the zone of separated and weakly bound multipoles. The increase of spread of synchrotron frequencies reduces the zone separated multipoles owing to which the microwave bunch instability can be caused by more and more low-frequency resonators. In the microwave zone practically there is no stabilizing effect of synchrotron frequencies spread. The instability threshold of the bunched beam now - where exceeds the microwave level

  6. Relativistic centrifugal instability

    Science.gov (United States)

    Gourgouliatos, Konstantinos N.; Komissarov, Serguei S.

    2018-03-01

    Near the central engine, many astrophysical jets are expected to rotate about their axis. Further out they are expected to go through the processes of reconfinement and recollimation. In both these cases, the flow streams along a concave surface and hence, it is subject to the centrifugal force. It is well known that such flows may experience the centrifugal instability (CFI), to which there are many laboratory examples. The recent computer simulations of relativistic jets from active galactic nuclei undergoing the process of reconfinement show that in such jets CFI may dominate over the Kelvin-Helmholtz instability associated with velocity shear (Gourgouliatos & Komissarov). In this letter, we generalize the Rayleigh criterion for CFI in rotating fluids to relativistic flows using a heuristic analysis. We also present the results of computer simulations which support our analytic criterion for the case of an interface separating two uniformly rotating cylindrical flows. We discuss the difference between CFI and the Rayleigh-Taylor instability in flows with curved streamlines.

  7. Analyses of MHD instabilities

    International Nuclear Information System (INIS)

    Takeda, Tatsuoki

    1985-01-01

    In this article analyses of the MHD stabilities which govern the global behavior of a fusion plasma are described from the viewpoint of the numerical computation. First, we describe the high accuracy calculation of the MHD equilibrium and then the analysis of the linear MHD instability. The former is the basis of the stability analysis and the latter is closely related to the limiting beta value which is a very important theoretical issue of the tokamak research. To attain a stable tokamak plasma with good confinement property it is necessary to control or suppress disruptive instabilities. We, next, describe the nonlinear MHD instabilities which relate with the disruption phenomena. Lastly, we describe vectorization of the MHD codes. The above MHD codes for fusion plasma analyses are relatively simple though very time-consuming and parts of the codes which need a lot of CPU time concentrate on a small portion of the codes, moreover, the codes are usually used by the developers of the codes themselves, which make it comparatively easy to attain a high performance ratio on the vector processor. (author)

  8. Ion temperature gradient instability

    International Nuclear Information System (INIS)

    1989-01-01

    Anomalous ion thermal conductivity remains an open physics issue for the present generation of high temperature Tokamaks. It is generally believed to be due to Ion Temperature Gradient Instability (η i mode). However, it has been difficult, if not impossible to identify this instability and study the anomalous transport due to it, directly. Therefore the production and identification of the mode is pursued in the simpler and experimentally convenient configuration of the Columbia Linear Machine (CLM). CLM is a steady state machine which already has all the appropriate parameters, except η i . This parameter is being increased to the appropriate value of the order of 1 by 'feathering' a tungsten screen located between the plasma source and the experimental cell to flatten the density profile and appropriate redesign of heating antennas to steepen the ion temperature profile. Once the instability is produced and identified, a thorough study of the characteristics of the mode can be done via a wide range of variation of all the critical parameters: η i , parallel wavelength, etc

  9. Velocity Structure and 3D Finite Element Modeling for Critical Instability of Gas Hydrate-related Slipstream Submarine Slide, offshore Vancouver Island, Canada

    Science.gov (United States)

    LONG, S.; He, T.; Lan, K.; Spence, G.; Yelisetti, S.

    2016-12-01

    The previous study indicated that Slipstream submarine landslide is one of a gas hydrate-related slope failures on the frontal ridges of the Northern Cascadia accretionary margin, off Vancouver Island, Canada. The OBS data collected during SeaJade project were used to derive the subseafloor Vp & Vs structures. The anomalous high Vp of about 2.0 km/s at shallow depths of 100 (± 10) mbsf closely matches the estimated depth of the glide plane. The modelled Vs above the BSR at a depth of 265-275 mbsf is about 100-150 m/s higher than a theoretical 100% water saturated background value, indicating that the hydrate acts as part of the load-bearing matrix to increase the rigidity of the sediment. Also, the Vp & Vs above BSR both indicate a consistent 40% saturation of gas hydrate. On the basis of high accurate submarine bathymetry obtained by multibeam sounding system, the submarine landform before slump is reconstructed by comparing the slump headwall geometry with surrounding ridges. Using the elastic moduli determined from Vp & Vs, the stress status was calculated by the finite element method for different conditions and confirmed that the undersea sliding process related with gas hydrate starts from the toe of the slope and then progressively retreats to the place of current headwall, in a series of triangular blocks or wedges. The shear stress are then compared with the frame shear strength of geological model, which is critical for controlling slope stability of steep frontal ridges The simulation results found that the ridge was stable under its own weight, but gas hydrate saturation decrease and pore-water pressure increase will greatly reduce shear strength of sediments and may cause a landslide. Since the study area is in the earthquake belt, the large seismic acceleration will greatly affect pore pressure distribution within the ridge. The simulation results indicated that the shallow high-velocity gas hydrate layer coincident with glide plane depth is more

  10. Plasma Instability Based Compact Coherent Terahertz Radiation Sources

    National Research Council Canada - National Science Library

    Bakshi, P

    2004-01-01

    .... These are in good agreement with experiments carried out at TU Vienna. A sharp emission line was obtained in the most recent structure, suggesting that we are close to the onset of plasma instability...

  11. Attitudes towards a final repository for the spent nuclear fuel. Structure and causes

    International Nuclear Information System (INIS)

    Sjoeberg, Lennart

    2008-09-01

    This report presents the results of a questionnaire survey of attitudes towards a final repository for the spent nuclear fuel. The questionnaire was mailed to 3,000 persons. Participants were young and older people in Oskarshamn municipality and Oesthammar municipality as well as in the rest of the country. Fifty-one percent responded. The questionnaire included a large number of questions of possible relevance for understanding the structure of and reasons for the person's attitude towards a final repository. Questions concerning nuclear power were dealt with in a special section. Men were more positively disposed towards a repository than women, older people more than young. The gender differences are mainly attributable to the variation in attitude towards nuclear power and concern about nuclear accidents. In the case of older people, interest was also a factor. Young people were not as interested in the issue. The most important factor in determining the attitude towards a final repository was the benefit it was expected to bring to the municipality. Moral and emotional aspects were also important. Risk played a relatively subordinate role. Social aspects were very important: those who frequently spoke with people who were positively disposed tended to be positive themselves, and vice versa for those who were negative. This factor could explain some of the gender differences in attitude. Attitudes in Oskarshamn were slightly more positive than in Oesthammar, probably due to the fact that the residents in Oskarshamn had a greater sense of participation in the municipality's decision in the matter. Information from SKB was also found to be an important factor for the differences in attitude between the municipalities. Eight percentage points more people had received information in Oskarshamn than in Oesthammar. The difference may be small, but it exists and does appear to be of some importance. Attitudes in Oskarshamn and Oesthammar continued to be much more

  12. Key performance outcomes of patient safety curricula: root cause analysis, failure mode and effects analysis, and structured communications skills.

    Science.gov (United States)

    Fassett, William E

    2011-10-10

    As colleges and schools of pharmacy develop core courses related to patient safety, course-level outcomes will need to include both knowledge and performance measures. Three key performance outcomes for patient safety coursework, measured at the course level, are the ability to perform root cause analyses and healthcare failure mode effects analyses, and the ability to generate effective safety communications using structured formats such as the Situation-Background-Assessment-Recommendation (SBAR) situational briefing model. Each of these skills is widely used in patient safety work and competence in their use is essential for a pharmacist's ability to contribute as a member of a patient safety team.

  13. Instability of expanding bacterial droplets.

    Science.gov (United States)

    Sokolov, Andrey; Rubio, Leonardo Dominguez; Brady, John F; Aranson, Igor S

    2018-04-03

    Suspensions of motile bacteria or synthetic microswimmers, termed active matter, manifest a remarkable propensity for self-organization, and formation of large-scale coherent structures. Most active matter research deals with almost homogeneous in space systems and little is known about the dynamics of strongly heterogeneous active matter. Here we report on experimental and theoretical studies on the expansion of highly concentrated bacterial droplets into an ambient bacteria-free fluid. The droplet is formed beneath a rapidly rotating solid macroscopic particle inserted in the suspension. We observe vigorous instability of the droplet reminiscent of a violent explosion. The phenomenon is explained in terms of continuum first-principle theory based on the swim pressure concept. Our findings provide insights into the dynamics of active matter with strong density gradients and significantly expand the scope of experimental and analytic tools for control and manipulation of active systems.

  14. Chronic neck pain: making the connection between capsular ligament laxity and cervical instability.

    Science.gov (United States)

    Steilen, Danielle; Hauser, Ross; Woldin, Barbara; Sawyer, Sarah

    2014-01-01

    The use of conventional modalities for chronic neck pain remains debatable, primarily because most treatments have had limited success. We conducted a review of the literature published up to December 2013 on the diagnostic and treatment modalities of disorders related to chronic neck pain and concluded that, despite providing temporary relief of symptoms, these treatments do not address the specific problems of healing and are not likely to offer long-term cures. The objectives of this narrative review are to provide an overview of chronic neck pain as it relates to cervical instability, to describe the anatomical features of the cervical spine and the impact of capsular ligament laxity, to discuss the disorders causing chronic neck pain and their current treatments, and lastly, to present prolotherapy as a viable treatment option that heals injured ligaments, restores stability to the spine, and resolves chronic neck pain. The capsular ligaments are the main stabilizing structures of the facet joints in the cervical spine and have been implicated as a major source of chronic neck pain. Chronic neck pain often reflects a state of instability in the cervical spine and is a symptom common to a number of conditions described herein, including disc herniation, cervical spondylosis, whiplash injury and whiplash associated disorder, postconcussion syndrome, vertebrobasilar insufficiency, and Barré-Liéou syndrome. When the capsular ligaments are injured, they become elongated and exhibit laxity, which causes excessive movement of the cervical vertebrae. In the upper cervical spine (C0-C2), this can cause a number of other symptoms including, but not limited to, nerve irritation and vertebrobasilar insufficiency with associated vertigo, tinnitus, dizziness, facial pain, arm pain, and migraine headaches. In the lower cervical spine (C3-C7), this can cause muscle spasms, crepitation, and/or paresthesia in addition to chronic neck pain. In either case, the presence of

  15. Sausage instability threshold in a low energy plasma focus

    International Nuclear Information System (INIS)

    Zakaullah, M.; Nasir, M.; Khattak, F.Y.; Murtaza, G.

    1993-01-01

    Development of sausage instability (m = 0 mode) is studied in a small low energy Mather-type plasma focus. A shadow graphic study of the current sheath has shown that the focused plasma necks off during the radial phase before the maximum compression. This may indicate the lowering of the instability threshold. Three hook-type structures are observed which may not be due to the multifoci formation. The bubble shape structure is observed to be developed in the expansion phase. (author)

  16. Structural changes in a clay-containing nanocomposite with a different moisture content caused by its deformation

    International Nuclear Information System (INIS)

    Fajtel'son, E.A.; Glaskova, T.I.; Korkhovm, V.P.; Aniskevich, A.N.

    2010-01-01

    This paper presents the results of an investigation of the properties of a clay-containing nanocomposite with an epoxy binder under moisture-temperature and mechanical action. It has been established that whatever the moisture content, the nanocomposite crystallizes under the thermomechanical action (upon reaching the glasstransition temperature). When the nanocomposite is heated to 70 C, the restructuring process is reversible, and its heating to above 150 C leads to its amorphization. The presence of clay nanoparticles (up to 6 mass percent) does not influence the temperature of structural transitions of the nanocomposite and does not cause a substantial strengthening effect. The sorbed moisture plasticizes the nanocomposite and decreases its glasstransition temperature by 10 C. The specific features of the thermomechanical behavior of nanocomposites upon their tensile prestrain or creep are due to the formation of an oriented structure. Their crystallization begins at lower temperatures and with a higher degree of crystallinity than that of unloaded nanostructures. (authors)

  17. Gravity Wave Dynamics in a Mesospheric Inversion Layer: 1. Reflection, Trapping, and Instability Dynamics

    Science.gov (United States)

    Laughman, Brian; Wang, Ling; Lund, Thomas S.; Collins, Richard L.

    2018-01-01

    Abstract An anelastic numerical model is employed to explore the dynamics of gravity waves (GWs) encountering a mesosphere inversion layer (MIL) having a moderate static stability enhancement and a layer of weaker static stability above. Instabilities occur within the MIL when the GW amplitude approaches that required for GW breaking due to compression of the vertical wavelength accompanying the increasing static stability. Thus, MILs can cause large‐amplitude GWs to yield instabilities and turbulence below the altitude where they would otherwise arise. Smaller‐amplitude GWs encountering a MIL do not lead to instability and turbulence but do exhibit partial reflection and transmission, and the transmission is a smaller fraction of the incident GW when instabilities and turbulence arise within the MIL. Additionally, greater GW transmission occurs for weaker MILs and for GWs having larger vertical wavelengths relative to the MIL depth and for lower GW intrinsic frequencies. These results imply similar dynamics for inversions due to other sources, including the tropopause inversion layer, the high stability capping the polar summer mesopause, and lower frequency GWs or tides having sufficient amplitudes to yield significant variations in stability at large and small vertical scales. MILs also imply much stronger reflections and less coherent GW propagation in environments having significant fine structure in the stability and velocity fields than in environments that are smoothly varying. PMID:29576994

  18. Instability of warped discs

    Science.gov (United States)

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

    2018-05-01

    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 that would generally encapsulate the classical Lightman-Eardley instability in planar discs (given by ∂(νΣ)/∂Σ < 0) but is here modified by the warp to include ∂(ν1|ψ|)/∂|ψ| < 0, and (2) a similar 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.

  19. Neuromuscular control and ankle instability.

    Science.gov (United States)

    Gutierrez, Gregory M; Kaminski, Thomas W; Douex, Al T

    2009-04-01

    Lateral ankle sprains (LAS) are common injuries in athletics and daily activity. Although most are resolved with conservative treatment, others develop chronic ankle instability (AI)-a condition associated with persistent pain, weakness, and instability-both mechanical (such as ligamentous laxity) and functional (neuromuscular impairment with or without mechanical laxity). The predominant theory in AI is one of articular deafferentation from the injury, affecting closed-loop (feedback/reflexive) neuromuscular control, but recent research has called that theory into question. A considerable amount of attention has been directed toward understanding the underlying causes of this pathology; however, little is known concerning the neuromuscular mechanisms behind the development of AI. The purpose of this review is to summarize the available literature on neuromuscular control in uninjured individuals and individuals with AI. Based on available research and reasonable speculation, it seems that open-loop (feedforward/anticipatory) neuromuscular control may be more important for the maintenance of dynamic joint stability than closed-loop control systems that rely primarily on proprioception. Therefore, incorporating perturbation activities into patient rehabilitation schemes may be of some benefit in enhancing these open-loop control mechanisms. Despite the amount of research conducted in this area, analysis of individuals with AI during dynamic conditions is limited. Future work should aim to evaluate dynamic perturbations in individuals with AI, as well as subjects who have a history of at least one LAS and never experienced recurrent symptoms. These potential findings may help elucidate some compensatory mechanisms, or more appropriate neuromuscular control strategies after an LAS event, thus laying the groundwork for future intervention studies that can attempt to reduce the incidence and severity of acute and chronic lateral ankle injury.

  20. System Detects Vibrational Instabilities

    Science.gov (United States)

    Bozeman, Richard J., Jr.

    1990-01-01

    Sustained vibrations at two critical frequencies trigger diagnostic response or shutdown. Vibration-analyzing electronic system detects instabilities of combustion in rocket engine. Controls pulse-mode firing of engine and identifies vibrations above threshold amplitude at 5.9 and/or 12kHz. Adapted to other detection and/or control schemes involving simultaneous real-time detection of signals above or below preset amplitudes at two or more specified frequencies. Potential applications include rotating machinery and encoders and decoders in security systems.

  1. 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.

  2. Collective instabilities of self-gravitating systems, 2

    International Nuclear Information System (INIS)

    Nakamura, Takashi; Takahara, Fumio; Ikeuchi, Satoru

    1975-01-01

    The instability modes of rotating self-gravitating systems are investigated on the assumption of infinitely long cylinder. The systems under consideration are a collisionless stellar system with anisotropic velocity dispersion and a gaseous system with anisotropic pressure. In the collisionless stellar system, the Jeans instability mode and the Harris instability mode exist. The dispersion relation is solved numerically and the following results are obtained: the Harris instability occurs even in the region where Wu did not treat, and although its growth rate amounts to the order of angular velocity of the system for sufficient anisotropy, the Harris instability always accompanies the Jeans instability and the latter is always greater than the former in growth rate. In the gaseous system exist the Jeans instability mode and a certain overstable mode, which are different from the Harris instability mode. It is shown that the overstable mode occurs due to coupling of modes. In relation to these results, some problems in galactic structure are discussed. (auth.)

  3. Resonant Drag Instabilities in protoplanetary disks: the streaming instability and new, faster-growing instabilities

    Science.gov (United States)

    Squire, Jonathan; Hopkins, Philip F.

    2018-04-01

    We identify and study a number of new, rapidly growing instabilities of dust grains in protoplanetary disks, which may be important for planetesimal formation. The study is based on the recognition that dust-gas mixtures are generically unstable to a Resonant Drag Instability (RDI), whenever the gas, absent dust, supports undamped linear modes. We show that the "streaming instability" is an RDI associated with epicyclic oscillations; this provides simple interpretations for its mechanisms and accurate analytic expressions for its growth rates and fastest-growing wavelengths. We extend this analysis to more general dust streaming motions and other waves, including buoyancy and magnetohydrodynamic oscillations, finding various new instabilities. Most importantly, we identify the disk "settling instability," which occurs as dust settles vertically into the midplane of a rotating disk. For small grains, this instability grows many orders of magnitude faster than the standard streaming instability, with a growth rate that is independent of grain size. Growth timescales for realistic dust-to-gas ratios are comparable to the disk orbital period, and the characteristic wavelengths are more than an order of magnitude larger than the streaming instability (allowing the instability to concentrate larger masses). This suggests that in the process of settling, dust will band into rings then filaments or clumps, potentially seeding dust traps, high-metallicity regions that in turn seed the streaming instability, or even overdensities that coagulate or directly collapse to planetesimals.

  4. Thermal instability of the trimeric structure of the N-terminal propeptide of human procollagen type I in relation to assay technology

    DEFF Research Database (Denmark)

    Brandt, J; Krogh, T N; Jensen, Charlotte Harken

    1999-01-01

    to measure the low-molecular weight form. Thermal transition of the high-molecular weight form caused a change in its elution volume but did not change its migration in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Mass spectrometry revealed identical results for both forms. We reached...

  5. Feedback stabilization of plasma instabilities

    International Nuclear Information System (INIS)

    Cap, F.F.

    1977-01-01

    This paper reviews the theoretical and experimental aspects of feedback stabilization. After giving an outline of a general theoretical model for electrostatic instabilities the author provides a theoretical analysis of the suppression of various types of instability. Experiments which have been carried out on the feedback stabilization of various types of plasma instability are reported. An extensive list of references is given. (B.R.H.)

  6. Thermal Shrinkage for Shoulder Instability

    OpenAIRE

    Toth, Alison P.; Warren, Russell F.; Petrigliano, Frank A.; Doward, David A.; Cordasco, Frank A.; Altchek, David W.; O’Brien, Stephen J.

    2010-01-01

    Thermal capsular shrinkage was popular for the treatment of shoulder instability, despite a paucity of outcomes data in the literature defining the indications for this procedure or supporting its long-term efficacy. The purpose of this study was to perform a clinical evaluation of radiofrequency thermal capsular shrinkage for the treatment of shoulder instability, with a minimum 2-year follow-up. From 1999 to 2001, 101 consecutive patients with mild to moderate shoulder instability underwent...

  7. Political Instability and Economic Growth

    OpenAIRE

    Alberto Alesina; Sule Ozler; Nouriel Roubini; Phillip Swagel

    1992-01-01

    This paper investigates the relationship between political instability and per capita GDP growth in a sample of 113 countries for the period 1950-1982. We define ?political instability? as the propensity of a government collapse, and we estimate a model in which political instability and economic growth are jointly determined. The main result of this paper is that in countries and time periods with a high propensity of government collapse, growth is significantly lower than otherwise. This ef...

  8. Width of electromagnetic wave instability spectrum in tungsten plate

    International Nuclear Information System (INIS)

    Rinkevich, A.B.

    1995-01-01

    Based on the study of high-frequency signal modulation and spectrum analysis of the envelope a measurement of spectrum width for electromagnetic wave instability was carried out under conditions of current pulse action on tungsten plate in magnetic field. The existence of amplitude-frequency wave modulation was revealed. The width of current disturbance spectrum in a specimen was evaluated. Current disturbances are shown to cause the instability of electromagnetic wave. 11 refs.; 6 figs

  9. Instabilities in mimetic matter perturbations

    Energy Technology Data Exchange (ETDEWEB)

    Firouzjahi, Hassan; Gorji, Mohammad Ali [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Mansoori, Seyed Ali Hosseini, E-mail: firouz@ipm.ir, E-mail: gorji@ipm.ir, E-mail: shosseini@shahroodut.ac.ir, E-mail: shossein@ipm.ir [Physics Department, Shahrood University of Technology, P.O. Box 3619995161 Shahrood (Iran, Islamic Republic of)

    2017-07-01

    We study cosmological perturbations in mimetic matter scenario with a general higher derivative function. We calculate the quadratic action and show that both the kinetic term and the gradient term have the wrong sings. We perform the analysis in both comoving and Newtonian gauges and confirm that the Hamiltonians and the associated instabilities are consistent with each other in both gauges. The existence of instabilities is independent of the specific form of higher derivative function which generates gradients for mimetic field perturbations. It is verified that the ghost instability in mimetic perturbations is not associated with the higher derivative instabilities such as the Ostrogradsky ghost.

  10. Instability of a cantilevered flexible plate in viscous channel flow

    Science.gov (United States)

    Balint, T. S.; Lucey, A. D.

    2005-10-01

    The stability of a flexible cantilevered plate in viscous channel flow is studied as a representation of the dynamics of the human upper airway. The focus is on instability mechanisms of the soft palate (flexible plate) that cause airway blockage during sleep. We solve the Navier Stokes equations for flow with Reynolds numbers up to 1500 fully coupled with the dynamics of the plate motion solved using finite-differences. The study is 2-D and based upon linearized plate mechanics. When both upper and lower airways are open, the plate is found to lose its stability through a flutter mechanism and a critical Reynolds number exists. When one airway is closed, the plate principally loses its stability through a divergence mechanism and a critical flow speed exists. However, below the divergence-onset flow speed, flutter can exist for low levels of structural damping in the flexible plate. Our results serve to extend understanding of flow-induced instability of cantilevered flexible plates and will ultimately improve the diagnosis and treatment of upper-airway disorders.

  11. Orbital Instabilities in a Triaxial Cusp Potential

    Science.gov (United States)

    Adams, Fred C.; Bloch, Anthony M.; Butler, Suzanne C.; Druce, Jeffrey M.; Ketchum, Jacob A.

    2007-12-01

    This paper constructs an analytic form for a triaxial potential that describes the dynamics of a wide variety of astrophysical systems, including the inner portions of dark matter halos, the central regions of galactic bulges, and young embedded star clusters. Specifically, this potential results from a density profile of the form ρ(m)~m-1, where the radial coordinate is generalized to triaxial form so that m2=x2/a2+y2/b2+z2/c2. Using the resulting analytic form of the potential and the corresponding force laws, we construct orbit solutions and show that a robust orbit instability exists in these systems. For orbits initially confined to any of the three principal planes, the motion in the perpendicular direction can be unstable. We discuss the range of parameter space for which these orbits are unstable, find the growth rates and saturation levels of the instability, and develop a set of analytic model equations that elucidate the essential physics of the instability mechanism. This orbit instability has a large number of astrophysical implications and applications, including understanding the formation of dark matter halos, the structure of galactic bulges, the survival of tidal streams, and the early evolution of embedded star clusters.

  12. Secular instabilities of Keplerian stellar discs

    Science.gov (United States)

    Kaur, Karamveer; Kazandjian, Mher V.; Sridhar, S.; Touma, Jihad R.

    2018-05-01

    We present idealized models of a razor-thin, axisymmetric, Keplerian stellar disc around a massive black hole, and study non-axisymmetric secular instabilities in the absence of either counter-rotation or loss cones. These discs are prograde mono-energetic waterbags, whose phase-space distribution functions are constant for orbits within a range of eccentricities (e) and zero outside this range. The linear normal modes of waterbags are composed of sinusoidal disturbances of the edges of distribution function in phase space. Waterbags that include circular orbits (polarcaps) have one stable linear normal mode for each azimuthal wavenumber m. The m = 1 mode always has positive pattern speed and, for polarcaps consisting of orbits with e normal modes for each m, which can be stable or unstable. We derive analytical expressions for the instability condition, pattern speeds, growth rates, and normal mode structure. Narrow bands are unstable to modes with a wide range in m. Numerical simulations confirm linear theory and follow the non-linear evolution of instabilities. Long-time integration suggests that instabilities of different m grow, interact non-linearly, and relax collisionlessly to a coarse-grained equilibrium with a wide range of eccentricities.

  13. 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.

  14. Integrated Component and System Analyses of Instabilities in Test Stands, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Instabilities associated with fluid handling and operation in liquid rocket propulsion systems and test facilities usually manifest themselves as structural...

  15. Transmission of chromosomal and instability via a chromosome irradiated with ionizing radiation

    International Nuclear Information System (INIS)

    Kodama, Seiji; Tanabe, Masateru; Shiraishi, Kazunori; Oshimura, Mitsuo

    2010-01-01

    We examined the stability of the transferred chromosome in 5 and 12 microcell hybrids including unirradiated human chromosomes 6 and 8, respectively, and 6 and 19 microcell hybrids including 4 Gy-irradiated human chromosomes 6 and 8, respectively. The transferred chromosome was structurally stable in most microcell hybrids transferred with the unirradiated chromosomes 6 and 8. In contrast, the 4 Gy-irradiated human chromosomes were unstable in 3 out of 6 hybrids (50%) with chromosome 6 and 3 out of 19 hybrids (16%) with chromosome 8, showing multiple aberrations in high frequencies (35∼98%). To know the cause of delayed chromosomal instability, intrachromosomal rearrangements of the human chromosome is investigated by subtelomere FISH in 17 microcell hybrids transferred with chromosomes 6 and 8. We found frequent intrachromosomal in 7 microcell hybrids (41%). However, no clear correlation was observed between the intrachromosomal rearrangements and the induction of delayed chromosomal instability by ionizing radiation

  16. Double Arc Instability in the Solar Corona

    Energy Technology Data Exchange (ETDEWEB)

    Ishiguro, N.; Kusano, K., E-mail: n-ishiguro@isee.nagoya-u.ac.jp [Institute for Space-Earth Environmental Research, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601 Japan (Japan)

    2017-07-10

    The stability of the magnetic field in the solar corona is important for understanding the causes of solar eruptions. Although various scenarios have been suggested to date, the tether-cutting reconnection scenario proposed by Moore et al. is one of the widely accepted models to explain the onset process of solar eruptions. Although the tether-cutting reconnection scenario proposes that the sigmoidal field formed by internal reconnection is the magnetic field in the pre-eruptive state, the stability of the sigmoidal field has not yet been investigated quantitatively. In this paper, in order to elucidate the stability problem of the pre-eruptive state, we developed a simple numerical analysis in which the sigmoidal field is modeled by a double arc electric current loop and its stability is analyzed. As a result, we found that the double arc loop is more easily destabilized than the axisymmetric torus, and it becomes unstable even if the external field does not decay with altitude, which is in contrast to the axisymmetric torus instability. This suggests that tether-cutting reconnection may well work as the onset mechanism of solar eruptions, and if so, the critical condition for eruption under a certain geometry may be determined by a new type of instability rather than by the torus instability. Based on them, we propose a new type of instability called double arc instability (DAI). We discuss the critical conditions for DAI and derive a new parameter κ , defined as the product of the magnetic twist and the normalized flux of the tether-cutting reconnection.

  17. Instability characteristics of fluidelastic instability of tube rows in crossflow

    International Nuclear Information System (INIS)

    Chen, S.S.; Jendrzejczyk, J.A.

    1986-04-01

    An experimental study is reported to investigate the jump phenomenon in critical flow velocities for tube rows with different pitch-to-diameter ratios and the excited and intrinsic instabilities for a tube row with a pitch-to-diameter ratio of 1.75. The experimental data provide additional insights into the instability phenomena of tube arrays in crossflow. 9 refs., 10 figs

  18. The Effect of Fin Pitch on Fluid Elastic Instability of Tube Arrays Subjected to Cross Flow of Water

    Science.gov (United States)

    Desai, Sandeep Rangrao; Pavitran, Sampat

    2018-02-01

    Failure of tubes in shell and tube exchangers is attributed to flow induced vibrations of such tubes. There are different excitations mechanisms due to which flow induced vibration occurs and among such mechanisms, fluid elastic instability is the most prominent one as it causes the most violent vibrations and may lead to rapid tube failures within short time. Fluid elastic instability is the fluid-structure interaction phenomenon which occurs when energy input by the fluid force exceeds energy expended in damping. This point is referred as instability threshold and corresponding velocity is referred as critical velocity. Once flow velocity exceeds critical flow velocity, the vibration amplitude increases very rapidly with flow velocity. An experimental program is carried out to determine the critical velocity at instability for plain and finned tube arrays subjected to cross flow of water. The tube array geometry is parallel triangular with cantilever end condition and pitch ratios considered are 2.6 and 2.1. The objective of research is to determine the effect of increase in pitch ratio on instability threshold for plain tube arrays and to assess the effect of addition of fins as well as increase in fin density on instability threshold for finned tube arrays. Plain tube array with two different pitch ratios; 2.1 and 2.6 and finned tube arrays with same pitch ratio; 2.6 but with two different fin pitches; such as fine (10 fpi) and coarse (4 fpi) are considered for the experimentation. Connors' equation that relates critical velocity at instability to different parameters, on which instability depends, has been used as the basis for analysis and the concept of effective diameter is used for the present investigation. The modal parameters are first suitably modified using natural frequency reduction setup that is already designed and developed to reduce natural frequency and hence to achieve experimental simulation of fluid elastic instability within the limited

  19. Studies of intense-laser plasma instabilities

    Czech Academy of Sciences Publication Activity Database

    Láska, Leoš; Krása, Josef; Badziak, J.; Jungwirth, Karel; Krouský, Eduard; Margarone, Daniele; Parys, P.

    2013-01-01

    Roč. 272, May (2013), 94-98 ISSN 0169-4332 R&D Projects: GA MŠk(CZ) 7E09092; GA MŠk(CZ) LC528; GA AV ČR IAA100100715 Institutional research plan: CEZ:AV0Z10100523 Keywords : laser plasma instabilities * self-generated magnetic field * longitudinal structure of the expanding plasma Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 2.538, year: 2013

  20. Kinetic instabilities in relativistic plasmas: the Harris instability revisited

    International Nuclear Information System (INIS)

    Tautz, R.C.

    2008-01-01

    Plasma instabilities that generate aperiodic fluctuations are of outstanding importance in the astrophysical context. Two prominent examples are the electromagnetic Weibel instability and the electrostatic Harris instability, which operate in initially non-magnetized and magnetized plasmas, respectively. In this talk, the original formulation of the Harris instability will be reviewed and generalizations will be presented such as the inclusion of (1) relativistic effects, (2) ion effects, and (3) mode coupling. It will be shown that, with these modifications, a powerful method has been developed for the determination of both the existence and the growth rate of low-frequency instabilities. Applications can be found in astrophysical jets, where the rest frame can be used and so no parallel motion is present. At the end of the talk, how the particle composition of gamma-ray burst jets can be predicted using the Harris technique. (author)

  1. Evaluation of corrosion caused by the use of in natura biogas in steam generator boilers of carbon steel structural elements

    Energy Technology Data Exchange (ETDEWEB)

    Fontenelle, Marcellus; Alves, Helton Jose, E-mail: helquimica@gmail.com [Universidade Estadual do Oeste do Parana (UNIOESTE), Cascavel, PR (Brazil); Pellizzer, Eder Luis [Universidade do Oeste de Santa Catarina (UNOESC), Xanxere, SC (Brazil); Monteiro, Marcos Roberto; Rovere, Carlos Alberto Della [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil); Higa, Silvia Midori [Universidade Tecnologica Federal do Parana (UTFPR), Londrina, PR (Brazil); Fontenelle, Isaddora [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)

    2017-05-15

    This work evaluates the corrosion process caused by the presence of hydrogen sulfide in the biogas in natura, in steels commonly used in the construction of steam generator boilers, simulating conditions close to those found on the real application of these materials, exposing the test bodies directly to biogas in natura, flame of combustion and gases resulting from the combustion of this biofuel, in chimney. After 314 hours of exposure under the specified conditions, the corroded surfaces of ASTM A178 and ASTM A516 were analyzed, by optical microscopy, electronic scanning microscopy, X-ray diffraction and surface hardness. The determination of corrosion rates for each test condition and each material tested can be used as a parameter for the determination of the minimum tolerance for mechanical stability, in the calculation of the minimum required thickness of the structural elements of the steam generator boilers fed to biogas. (author)

  2. Evaluation of corrosion caused by the use of in natura biogas in steam generator boilers of carbon steel structural elements

    International Nuclear Information System (INIS)

    Fontenelle, Marcellus; Alves, Helton Jose; Pellizzer, Eder Luis; Monteiro, Marcos Roberto; Rovere, Carlos Alberto Della; Higa, Silvia Midori; Fontenelle, Isaddora

    2017-01-01

    This work evaluates the corrosion process caused by the presence of hydrogen sulfide in the biogas in natura, in steels commonly used in the construction of steam generator boilers, simulating conditions close to those found on the real application of these materials, exposing the test bodies directly to biogas in natura, flame of combustion and gases resulting from the combustion of this biofuel, in chimney. After 314 hours of exposure under the specified conditions, the corroded surfaces of ASTM A178 and ASTM A516 were analyzed, by optical microscopy, electronic scanning microscopy, X-ray diffraction and surface hardness. The determination of corrosion rates for each test condition and each material tested can be used as a parameter for the determination of the minimum tolerance for mechanical stability, in the calculation of the minimum required thickness of the structural elements of the steam generator boilers fed to biogas. (author)

  3. An Emerging Tick-Borne Disease of Humans Is Caused by a Subset of Strains with Conserved Genome Structure

    Science.gov (United States)

    Barbet, Anthony F.; Al-Khedery, Basima; Stuen, Snorre; Granquist, Erik G.; Felsheim, Roderick F.; Munderloh, Ulrike G.

    2013-01-01

    The prevalence of tick-borne diseases is increasing worldwide. One such emerging disease is human anaplasmosis. The causative organism, Anaplasma phagocytophilum, is known to infect multiple animal species and cause human fatalities in the U.S., Europe and Asia. Although long known to infect ruminants, it is unclear why there are increasing numbers of human infections. We analyzed the genome sequences of strains infecting humans, animals and ticks from diverse geographic locations. Despite extensive variability amongst these strains, those infecting humans had conserved genome structure including the pfam01617 superfamily that encodes the major, neutralization-sensitive, surface antigen. These data provide potential targets to identify human-infective strains and have significance for understanding the selective pressures that lead to emergence of disease in new species. PMID:25437207

  4. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation

    DEFF Research Database (Denmark)

    Minjoli, Sena; Saturnino, Guilherme B.; Blicher, Jakob Udby

    2017-01-01

    aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible....... Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative...... to the lesion were tested. For TDCS, the finite-element method was used to simulate a standard approach with two electrode pads, and the position of one electrode was systematically varied. For both TMS and TDCS, the lesion caused electric field " hot spots" in the cortex. However, these maxima were...

  5. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation

    DEFF Research Database (Denmark)

    Minjoli, Sena; Saturnino, Guilherme B.; Blicher, Jakob Udby

    2017-01-01

    Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (TDCS) are two types of non-invasive transcranial brain stimulation (TBS). They are useful tools for stroke research and may be potential adjunct therapies for functional recovery. However, stroke often causes large...... cerebral lesions, which are commonly accompanied by a secondary enlargement of the ventricles and atrophy. These structural alterations substantially change the conductivity distribution inside the head, which may have potentially important consequences for both brain stimulation methods. We therefore....... Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative...

  6. Water level measurement uncertainty during BWR instability

    International Nuclear Information System (INIS)

    Torok, R.C.; Derbidge, T.C.; Healzer, J.M.

    1994-01-01

    This paper addresses the performance of the water-level measurement system in a boiling water reactor (BWR) during severe instability oscillations which, under some circumstances, can occur during an anticipated transient without SCRAM (ATWS). Test data from a prototypical mock-up of the water-level measurement system was used to refine and calibrate a water-level measurement system model. The model was then used to predict level measurement system response, using as boundary conditions vessel pressures calculated by ppercase RETRAN for an ATWS/instability event.The results of the study indicate that rapid pressure changes in the reactor pressure vessel which cause oscillations in downcomer water level, coupled with differences in instrument line lengths, can produce errors in the sensed water level. Using nominal parameters for the measurement system components, a severe instability transient which produced a 0.2 m peak-to-minimum water-level oscillation in the vessel downcomer was predicted to produce pressure difference equivalent to a 0.7 m level oscillation at the input to the differential pressure transmitter, 0.5 m oscillation at the output of the transmitter, and an oscillation of 0.3 m on the water-level indicator in the control room. The level measurement system error, caused by downcomer water-level oscillations and instrument line length differential, is mitigated by damping both in the differential pressure transmitter used to infer level and in the control room display instrument. ((orig.))

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

    KAUST Repository

    Reis, T.; Wilson, H.J.

    2013-01-01

    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. 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.

  9. Structure of the Elastin-Contractile Units in the Thoracic Aorta and How Genes That Cause Thoracic Aortic Aneurysms and Dissections Disrupt This Structure.

    Science.gov (United States)

    Karimi, Ashkan; Milewicz, Dianna M

    2016-01-01

    The medial layer of the aorta confers elasticity and strength to the aortic wall and is composed of alternating layers of smooth muscle cells (SMCs) and elastic fibres. The SMC elastin-contractile unit is a structural unit that links the elastin fibres to the SMCs and is characterized by the following: (1) layers of elastin fibres that are surrounded by microfibrils; (2) microfibrils that bind to the integrin receptors in focal adhesions on the cell surface of the SMCs; and (3) SMC contractile filaments that are linked to the focal adhesions on the inner side of the membrane. The genes that are altered to cause thoracic aortic aneurysms and aortic dissections encode proteins involved in the structure or function of the SMC elastin-contractile unit. Included in this gene list are the genes encoding protein that are structural components of elastin fibres and microfibrils, FBN1, MFAP5, ELN, and FBLN4. Also included are genes that encode structural proteins in the SMC contractile unit, including ACTA2, which encodes SMC-specific α-actin and MYH11, which encodes SMC-specific myosin heavy chain, along with MYLK and PRKG1, which encode kinases that control SMC contraction. Finally, mutations in the gene encoding the protein linking integrin receptors to the contractile filaments, FLNA, also predispose to thoracic aortic disease. Thus, these data suggest that functional SMC elastin-contractile units are important for maintaining the structural integrity of the aorta. Copyright © 2016 Canadian Cardiovascular Society. Published by Elsevier Inc. All rights reserved.

  10. Magmatic structures in the Krkonoše Jizera Plutonic Complex, Bohemian Massif: evidence for localized multiphase flow and small-scale thermal mechanical instabilities in a granitic magma chamber

    Science.gov (United States)

    Žák, Jiří; Klomínský, Josef

    2007-08-01

    The present paper examines magmatic structures in the Jizera and Liberec granites of the Krkonoše-Jizera Plutonic Complex, Bohemian Massif. The magmatic structures are here interpreted to preserve direct field evidence for highly localized magma flow and other processes in crystal-rich mushes, and to capture the evolution of physical processes in an ancient granitic magma chamber. We propose that after chamber-wide mixing and hybridization, as suggested by recent petrological studies, laminar magma flow became highly localized to weaker channel-like domains within the higher-strength crystal framework. Mafic schlieren formed at flow rims, and their formation presumably involved gravitational settling and velocity gradient flow sorting coupled with interstitial melt escape. Local thermal or compositional convection may have resulted in the formation of vertical schlieren tubes and ladder dikes whereas subhorizontal tubes or channels formed during flow driven by lateral gradients in magma pressure. After the cessation or deceleration of channel flow, gravity-driven processes (settling of crystals and enclaves, gravitational differentiation, development of downward dripping instabilities), accompanied by compaction, filter pressing and melt segregation, dominated in the crystal mush within the flow channels. Subsequently, magmatic folds developed in schlieren layers and the magma chamber recorded complex, late magmatic strains at high magma crystallinities. Late-stage magma pulsing into localized submagmatic cracks represents the latest events of magmatic history of the chamber prior to its final crystallization. We emphasize that the most favorable environments for the formation and preservation of magmatic structures, such as those hosted in the Jizera and Liberec granites, are slowly cooling crystal-rich mushes. Therefore, where preserved in plutons, these structures may lend strong support for a "mush model" of magmatic systems.

  11. 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. .

  12. 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.

  13. Simulation and quasilinear theory of proton firehose instability

    Energy Technology Data Exchange (ETDEWEB)

    Seough, Jungjoon [Korean Astronomy and Space Science Institute, Daejeon (Korea, Republic of); Faculty of Human Development, University of Toyama, 3190, Gofuku, Toyama City, Toyama, 930-8555 (Japan); Yoon, Peter H. [University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701 (Korea, Republic of); Hwang, Junga [Korean Astronomy and Space Science Institute, Daejeon (Korea, Republic of); Korea, University of Science and Technology, Daejeon (Korea, Republic of)

    2015-01-15

    The electromagnetic proton firehose instability is driven by excessive parallel temperature anisotropy, T{sub ∥} > T{sub ⊥} (or more precisely, parallel pressure anisotropy, P{sub ∥} > P{sub ⊥}) in high-beta plasmas. Together with kinetic instabilities driven by excessive perpendicular temperature anisotropy, namely, electromagnetic proton cyclotron and mirror instabilities, its role in providing the upper limit for the temperature anisotropy in the solar wind is well-known. A recent Letter [Seough et al., Phys. Rev. Lett. 110, 071103 (2013)] employed quasilinear kinetic theory for these instabilities to explain the observed temperature anisotropy upper bound in the solar wind. However, the validity of quasilinear approach has not been rigorously tested until recently. In a recent paper [Seough et al., Phys. Plasmas 21, 062118 (2014)], a comparative study is carried out for the first time in which quasilinear theory of proton cyclotron instability is tested against results obtained from the particle-in-cell simulation method, and it was demonstrated that the agreement was rather excellent. The present paper addresses the same issue involving the proton firehose instability. Unlike the proton cyclotron instability, however, it is found that the quasilinear approximation enjoys only a limited range of validity, especially for the wave dynamics and for the relatively high-beta regime. Possible causes and mechanisms responsible for the discrepancies are speculated and discussed.

  14. The nature of the Vela X-ray ``jet". The Rayleigh-Taylor instability and the origin of filamentary structures in the Vela supernova remnant

    Science.gov (United States)

    Gvaramadze, Vasilii

    1999-12-01

    The nature of the Vela X-ray ``jet", recently discovered by Markwardt & Ögelman (1995), is examined. It is suggested that the ``jet" arises along the interface of domelike deformations of the Rayleigh-Taylor unstable shell of the Vela supernova remnant; thereby the ``jet" is interpreted as a part of the general shell of the remnant. The origin of deformations as well as the general structure of the remnant are discussed in the framework of a model based on a cavity explosion of a supernova star. It is suggested that the shell deformations viewed at various angles appear as filamentary structures visible throughout the Vela supernova remnant at radio, optical, and X-ray wavelengths. A possible origin of the nebula of hard X-ray emission detected by Willmore et al. (1992) around the Vela pulsar is proposed.

  15. Instabilities in the aether

    International Nuclear Information System (INIS)

    Carroll, Sean M.; Dulaney, Timothy R.; Gresham, Moira I.; Tam, Heywood

    2009-01-01

    We investigate the stability of theories in which Lorentz invariance is spontaneously broken by fixed-norm vector 'aether' fields. Models with generic kinetic terms are plagued either by ghosts or by tachyons, and are therefore physically unacceptable. There are precisely three kinetic terms that are not manifestly unstable: a sigma model (∂ μ A ν ) 2 , the Maxwell Lagrangian F μν F μν , and a scalar Lagrangian (∂ μ A μ ) 2 . The timelike sigma-model case is well defined and stable when the vector norm is fixed by a constraint; however, when it is determined by minimizing a potential there is necessarily a tachyonic ghost, and therefore an instability. In the Maxwell and scalar cases, the Hamiltonian is unbounded below, but at the level of perturbation theory there are fewer degrees of freedom and the models are stable. However, in these two theories there are obstacles to smooth evolution for certain choices of initial data.

  16. From instabilities to multifragmentation

    International Nuclear Information System (INIS)

    Chomaz, P.; Jacquot, B.; Colonna, M.; Guarnera, A.

    1994-01-01

    The main purpose of this article is to show that, in many physical situations, the spinodal decomposition of unstable systems can be correctly described by stochastic mean-field approaches. Such theories predict that the occurrence of spinodal instability leading the multifragmentation of an expended nuclear system, can be signed through the observation of time scales for the fragment formation of the order of 100 fm/c and of typical fragment size around A=20. We will finally discuss the fact that these fragments are formed at finite temperature and so can subsequently decay in flight. Finally, we will give some hints about possible experimental signals of such first order phase transitions. (authors). 12 refs., 5 figs

  17. From instabilities to multifragmentation

    Energy Technology Data Exchange (ETDEWEB)

    Chomaz, P.; Jacquot, B. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France); Colonna, M.; Guarnera, A. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France)]|[Istituto Nazionale di Fisica Nucleare, Bologna (Italy)

    1994-12-31

    The main purpose of this article is to show that, in many physical situations, the spinodal decomposition of unstable systems can be correctly described by stochastic mean-field approaches. Such theories predict that the occurrence of spinodal instability leading the multifragmentation of an expended nuclear system, can be signed through the observation of time scales for the fragment formation of the order of 100 fm/c and of typical fragment size around A=20. We will finally discuss the fact that these fragments are formed at finite temperature and so can subsequently decay in flight. Finally, we will give some hints about possible experimental signals of such first order phase transitions. (authors). 12 refs., 5 figs.

  18. 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

  19. Competing Structural Instabilities in the Ruddlesden–Popper Derivatives HRTiO4 (R = Rare Earths): Oxygen Octahedral Rotations Inducing Noncentrosymmetricity and Layer Sliding Retaining Centrosymmetricity

    International Nuclear Information System (INIS)

    Sen Gupta, Arnab; Akamatsu, Hirofumi; Brown, Forrest G.; Nguyen, Minh An T.

    2016-01-01

    We report the discovery of noncentrosymmetry in the family of HRTiO 4 (R = Eu, Gd, Dy) layered oxides possessing a Ruddlesden-Popper derivative structure, by second harmonic generation and synchrotron x-ray diffraction with the support of density functional theory calculations. These oxides were previously thought to possess inversion symmetry. Here, inversion symmetry is broken by oxygen octahedral rotations, a mechanism that is not active in simple perovskites. We discover a competition between oxygen octahedral rotations and sliding of the octahedral perovskite blocks at the OH layers. For the smaller rare earth ions, R = Eu, Gd, Dy, which favor the octahedral rotations, noncentrosymmetry is present but the sliding at the OH layer is absent. For the larger rare earth ions, R = Nd and Sm, the octahe-dral rotations are absent, but sliding of the octahedral blocks at the OH layer is present, likely to optimize the hydrogen bond length arising from the directional nature of these bonds in the crystal structure. The study reveals a new mechanism for inducing noncentrosymmetry in layered oxides, and chemical-structural effects related to rare earth ion size and hydrogen bonding that can turn this mechanism on and off. In conclusion, we construct a complete phase diagram of temperature versus rare earth ionic radius for the HRTiO 4 family.

  20. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation

    Directory of Open Access Journals (Sweden)

    Sena Minjoli

    2017-01-01

    Full Text Available Transcranial magnetic stimulation (TMS and transcranial direct current stimulation (TDCS are two types of non-invasive transcranial brain stimulation (TBS. They are useful tools for stroke research and may be potential adjunct therapies for functional recovery. However, stroke often causes large cerebral lesions, which are commonly accompanied by a secondary enlargement of the ventricles and atrophy. These structural alterations substantially change the conductivity distribution inside the head, which may have potentially important consequences for both brain stimulation methods. We therefore aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible. Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative to the lesion were tested. For TDCS, the finite-element method was used to simulate a standard approach with two electrode pads, and the position of one electrode was systematically varied. For both TMS and TDCS, the lesion caused electric field “hot spots” in the cortex. However, these maxima were not substantially stronger than those seen in a healthy control. The electric field pattern induced by TMS was not substantially changed by the lesions. However, the average field strength generated by TDCS was substantially decreased. This effect occurred for both head models and even when both electrodes were distant to the lesion, caused by increased current shunting through the lesion and enlarged ventricles. Judging from the similar peak field strengths compared

  1. The impact of large structural brain changes in chronic stroke patients on the electric field caused by transcranial brain stimulation.

    Science.gov (United States)

    Minjoli, Sena; Saturnino, Guilherme B; Blicher, Jakob Udby; Stagg, Charlotte J; Siebner, Hartwig R; Antunes, André; Thielscher, Axel

    2017-01-01

    Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (TDCS) are two types of non-invasive transcranial brain stimulation (TBS). They are useful tools for stroke research and may be potential adjunct therapies for functional recovery. However, stroke often causes large cerebral lesions, which are commonly accompanied by a secondary enlargement of the ventricles and atrophy. These structural alterations substantially change the conductivity distribution inside the head, which may have potentially important consequences for both brain stimulation methods. We therefore aimed to characterize the impact of these changes on the spatial distribution of the electric field generated by both TBS methods. In addition to confirming the safety of TBS in the presence of large stroke-related structural changes, our aim was to clarify whether targeted stimulation is still possible. Realistic head models containing large cortical and subcortical stroke lesions in the right parietal cortex were created using MR images of two patients. For TMS, the electric field of a double coil was simulated using the finite-element method. Systematic variations of the coil position relative to the lesion were tested. For TDCS, the finite-element method was used to simulate a standard approach with two electrode pads, and the position of one electrode was systematically varied. For both TMS and TDCS, the lesion caused electric field "hot spots" in the cortex. However, these maxima were not substantially stronger than those seen in a healthy control. The electric field pattern induced by TMS was not substantially changed by the lesions. However, the average field strength generated by TDCS was substantially decreased. This effect occurred for both head models and even when both electrodes were distant to the lesion, caused by increased current shunting through the lesion and enlarged ventricles. Judging from the similar peak field strengths compared to the healthy

  2. Internal rotor friction instability

    Science.gov (United States)

    Walton, J.; Artiles, A.; Lund, J.; Dill, J.; Zorzi, E.

    1990-01-01

    The analytical developments and experimental investigations performed in assessing the effect of internal friction on rotor systems dynamic performance are documented. Analytical component models for axial splines, Curvic splines, and interference fit joints commonly found in modern high speed turbomachinery were developed. Rotor systems operating above a bending critical speed were shown to exhibit unstable subsynchronous vibrations at the first natural frequency. The effect of speed, bearing stiffness, joint stiffness, external damping, torque, and coefficient of friction, was evaluated. Testing included material coefficient of friction evaluations, component joint quantity and form of damping determinations, and rotordynamic stability assessments. Under conditions similar to those in the SSME turbopumps, material interfaces experienced a coefficient of friction of approx. 0.2 for lubricated and 0.8 for unlubricated conditions. The damping observed in the component joints displayed nearly linear behavior with increasing amplitude. Thus, the measured damping, as a function of amplitude, is not represented by either linear or Coulomb friction damper models. Rotordynamic testing of an axial spline joint under 5000 in.-lb of static torque, demonstrated the presence of an extremely severe instability when the rotor was operated above its first flexible natural frequency. The presence of this instability was predicted by nonlinear rotordynamic time-transient analysis using the nonlinear component model developed under this program. Corresponding rotordynamic testing of a shaft with an interference fit joint demonstrated the presence of subsynchronous vibrations at the first natural frequency. While subsynchronous vibrations were observed, they were bounded and significantly lower in amplitude than the synchronous vibrations.

  3. Dynamical Instability and Soliton Concept

    International Nuclear Information System (INIS)

    Kartavenko, V.G.

    1994-01-01

    The problem of dynamical instability and clustering (stable fragments formation) in a breakup of excited nuclear systems are considered from the points of view of the soliton concept. It is noted that the volume (spinodal) instability can be associated with nonlinear terms, and the surface (Rayleigh-Taylor type) instability, with the dispersion terms in the evolution equations. The spinodal instability and the Rayleigh-Taylor instability may compensate each other and lead to stable quasi-soliton type objects. The simple analytical model is presented to illustrate this physical picture. The time evolution of an initially compressed cold nuclear system is analysed in the framework of the inverse mean-field method. It is demonstrated that the nonlinearity and dispersion terms of the evolution equations can lead to clusterization in the final channel. 8 p

  4. Beam instability Workshop - plenary sessions

    International Nuclear Information System (INIS)

    2001-01-01

    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

  5. 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.

  6. Electron/electron acoustic instability

    International Nuclear Information System (INIS)

    Gary, S.P.

    1987-01-01

    The electron acoustic wave becomes a normal mode of an unmagnetized collisionless plasma in the presence of two electron components with similar densities, but strongly disparate temperatures. The characteristic frequency of this mode is the plasma frequency of the cooler electron component. If these two electron components have a relative drift speed several times the thermal speed of the cooler component, the electron/electron acoustic instability may arise. This paper describes the parametric dependences of the threshold drift speed and maximum growth rate of this instability, and compares these with the same properties of the electron/ion acoustic instability. Under the condition of zero current, the electron/ion acoustic instability typically has the lower threshold drift speed, so that observation of the electron/electron acoustic instability is a strong indication of the presence of an electrical current in the plasma

  7. Gravitational Instabilities in Circumstellar Disks

    Science.gov (United States)

    Kratter, Kaitlin; Lodato, Giuseppe

    2016-09-01

    Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review, we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small-scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability supplemented with a survey of numerical simulations that aim to capture the nonlinear evolution. We emphasize the role of thermodynamics and large-scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analytic predictions and numerical results. In the next part of our review, we focus on the astrophysical consequences of the instability. We show that the disks most likely to be gravitationally unstable are young and relatively massive compared with their host star, Md/M*≥0.1. They will develop quasi-stable spiral arms that process infall from the background cloud. Although instability is less likely at later times, once infall becomes less important, the manifestations of the instability are more varied. In this regime, the disk thermodynamics, often regulated by stellar irradiation, dictates the development and evolution of the instability. In some cases the instability may lead to fragmentation into bound companions. These companions are more likely to be brown dwarfs or stars than planetary mass objects. Finally, we highlight open questions related to the development of a turbulent cascade in thin disks and the role of mode-mode coupling in setting the maximum angular

  8. Thermal shrinkage for shoulder instability.

    Science.gov (United States)

    Toth, Alison P; Warren, Russell F; Petrigliano, Frank A; Doward, David A; Cordasco, Frank A; Altchek, David W; O'Brien, Stephen J

    2011-07-01

    Thermal capsular shrinkage was popular for the treatment of shoulder instability, despite a paucity of outcomes data in the literature defining the indications for this procedure or supporting its long-term efficacy. The purpose of this study was to perform a clinical evaluation of radiofrequency thermal capsular shrinkage for the treatment of shoulder instability, with a minimum 2-year follow-up. From 1999 to 2001, 101 consecutive patients with mild to moderate shoulder instability underwent shoulder stabilization surgery with thermal capsular shrinkage using a monopolar radiofrequency device. Follow-up included a subjective outcome questionnaire, discussion of pain, instability, and activity level. Mean follow-up was 3.3 years (range 2.0-4.7 years). The thermal capsular shrinkage procedure failed due to instability and/or pain in 31% of shoulders at a mean time of 39 months. In patients with unidirectional anterior instability and those with concomitant labral repair, the procedure proved effective. Patients with multidirectional instability had moderate success. In contrast, four of five patients with isolated posterior instability failed. Thermal capsular shrinkage has been advocated for the treatment of shoulder instability, particularly mild to moderate capsular laxity. The ease of the procedure makes it attractive. However, our retrospective review revealed an overall failure rate of 31% in 80 patients with 2-year minimum follow-up. This mid- to long-term cohort study adds to the literature lacking support for thermal capsulorrhaphy in general, particularly posterior instability. The online version of this article (doi:10.1007/s11420-010-9187-7) contains supplementary material, which is available to authorized users.

  9. Instability timescale for the inclination instability in the solar system

    Science.gov (United States)

    Zderic, Alexander; Madigan, Ann-Marie; Fleisig, Jacob

    2018-04-01

    The gravitational influence of small bodies is often neglected in the study of solar system dynamics. However, this is not always an appropriate assumption. For example, mutual secular torques between low mass particles on eccentric orbits can result in a self-gravity instability (`inclination instability'; Madigan & McCourt 2016). During the instability, inclinations increase exponentially, eccentricities decrease (detachment), and orbits cluster in argument of perihelion. In the solar system, the orbits of the most distant objects show all three of these characteristics (high inclination: Volk & Malhotra (2017), detachment: Delsanti & Jewitt (2006), and argument of perihelion clustering: Trujillo & Sheppard (2014)). The inclination instability is a natural explanation for these phenomena.Unfortunately, full N-body simulations of the solar system are unfeasible (N ≈ O(1012)), and the behavior of the instability depends on N, prohibiting the direct application of lower N simulations. Here we present the instability timescale's functional dependence on N, allowing us to extrapolate our simulation results to that appropriate for the solar system. We show that ~5 MEarth of small icy bodies in the Sedna region is sufficient for the inclination instability to occur in the outer solar system.

  10. 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.

  11. Canonical momenta and numerical instabilities in particle codes

    International Nuclear Information System (INIS)

    Godfrey, B.B.

    1975-01-01

    A set of warm plasma dispersion relations appropriate to a large class of electromagnetic plasma simulation codes is derived. The numerical Cherenkov instability is shown by analytic and numerical analysis of these dispersion relations to be the most significant nonphysical effect involving transverse electromagnetic waves. The instability arises due to a spurious phase shift between resonant particles and light waves, caused by a basic incompatibility between the Lagrangian treatment of particle positions and the Eulerian treatment of particle velocities characteristic of most PIC--CIC algorithms. It is demonstrated that, through the use of canonical momentum, this mismatch is alleviated sufficiently to completely eliminate the Cherenkov instability. Collateral effects on simulation accuracy and on other numerical instabilities appear to be minor

  12. Nutation instability of spinning solid rocket motor spacecraft

    Directory of Open Access Journals (Sweden)

    Dan YANG

    2017-08-01

    Full Text Available The variation of mass, and moment of inertia of a spin-stabilized spacecraft leads to concern about the nutation instability. Here a careful analysis on the nutation instability is performed on a spacecraft propelled by solid rocket booster (SRB. The influences of specific solid propellant designs on transversal angular velocity are discussed. The results show that the typical SRB of End Burn suppresses the non-principal axial angular velocity. On the contrary, the frequently used SRB of Radial Burn could amplify the transversal angular velocity. The nutation instability caused by a design of Radial Burn could be remedied by the addition of End Burn at the same time based on the study of the combination design of both End Burn and Radial Burn. The analysis of the results proposes the design conception of how to control the nutation motion. The method is suitable to resolve the nutation instability of solid rocket motor with complex propellant patterns.

  13. Simulations relevant to the beam instability in the foreshock

    International Nuclear Information System (INIS)

    Cairns, I.H.; Nishikawa, K.I.

    1989-01-01

    Electrons backstreaming into Earth's foreshock generate waves near the plasma frequency f p by the beam instability. Tow versions of the beam instability exist: the reactive version, in which narrow-band waves grow by bunching the electrons in space, and the kinetic version, in which broadband growth occurs by a maser mechanism. Recently, it has been suggested that (1) the backstreaming electrons have steep-sided cutoff distributions which are initially unstable to the reactive instability, (2) the back reaction to the wave growth causes the instability to pass into its kinetic phase, and (3) the kinetic instability saturates by quasi-linear relaxation. In this paper the authors present two-dimensional simulations of the reactive instability for Maxwellian beams and cutoff distributions. They demonstrate that the reactive instability is a bunching instability and that the reactive instability saturates and passes over into the kinetic phase by particle trapping.A reactive/kinetic transition is shown to most likely occur within 1 km and 50 km of the bow shock. They suggest that the frequency of the intense narrow-band waves decrease from above f p to perhaps 0.9f p (dependent on the beam density) with increasing penetration into the high beam speed region of the foreshock, before the wave frequency rises again as the waves become broadband deeper in the foreshock. Both the simulation results and numerical solutions of the dispersion equation indicate that for the observed beam parameters the center frequency of the waves near the foreshock boundary should be between 0.9f p and 0.98f p , rather than above f p as previously believed. The simulation results indicate that the effects of spatial inhomogeneity are vital for a quantitative understanding of the foreshock waves

  14. Numerical methods on flow instabilities in steam generator

    International Nuclear Information System (INIS)

    Yoshikawa, Ryuji; Hamada, Hirotsugu; Ohshima, Hiroyuki; Yanagisawa, Hideki

    2008-06-01

    The phenomenon of two-phase flow instability is important for the design and operation of many industrial systems and equipment, such as steam generators. The designer's job is to predict the threshold of flow instability in order to design around it or compensate for it. So it is essential to understand the physical phenomena governing such instability and to develop computational tools to model the dynamics of boiling systems. In Japan Atomic Energy Agency, investigations on heat transfer characteristics of steam generator are being performed for the development of Sodium-cooled Fast Breeder Reactor. As one part of the research work, the evaluations of two-phase flow instability in the steam generator are being carried out experimentally and numerically. In this report, the numerical methods were studied for two-phase flow instability analysis in steam generator. For numerical simulation purpose, the special algorithm to calculate inlet flow rate iteratively with inlet pressure and outlet pressure as boundary conditions for the density-wave instability analysis was established. There was no need to solve property derivatives and large matrices, so the spurious numerical instabilities caused by discontinuous property derivatives at boiling boundaries were avoided. Large time-step was possible. The flow instability in single heat transfer tube was successfully simulated with homogeneous equilibrium model by using the present algorithm. Then the drift-flux model including the effects of subcooled boiling and two phase slip was adopted to improve the accuracy. The computer code was developed after selecting the correlations of drift velocity and distribution parameter. The capability of drift flux model together with the present algorithm for simulating density-wave instability in single tube was confirmed. (author)

  15. Postural instability detection: aging and the complexity of spatial-temporal distributional patterns for virtually contacting the stability boundary in human stance.

    Directory of Open Access Journals (Sweden)

    Melissa C Kilby

    Full Text Available Falls among the older population can severely restrict their functional mobility and even cause death. Therefore, it is crucial to understand the mechanisms and conditions that cause falls, for which it is important to develop a predictive model of falls. One critical quantity for postural instability detection and prediction is the instantaneous stability of quiet upright stance based on motion data. However, well-established measures in the field of motor control that quantify overall postural stability using center-of-pressure (COP or center-of-mass (COM fluctuations are inadequate predictors of instantaneous stability. For this reason, 2D COP/COM virtual-time-to-contact (VTC is investigated to detect the postural stability deficits of healthy older people compared to young adults. VTC predicts the temporal safety margin to the functional stability boundary ( =  limits of the region of feasible COP or COM displacement and, therefore, provides an index of the risk of losing postural stability. The spatial directions with increased instability were also determined using quantities of VTC that have not previously been considered. Further, Lempel-Ziv-Complexity (LZC, a measure suitable for on-line monitoring of stability/instability, was applied to explore the temporal structure or complexity of VTC and the predictability of future postural instability based on previous behavior. These features were examined as a function of age, vision and different load weighting on the legs. The primary findings showed that for old adults the stability boundary was contracted and VTC reduced. Furthermore, the complexity decreased with aging and the direction with highest postural instability also changed in aging compared to the young adults. The findings reveal the sensitivity of the time dependent properties of 2D VTC to the detection of postural instability in aging, availability of visual information and postural stance and potential applicability as a

  16. Semiconductor Lasers Stability, Instability and Chaos

    CERN Document Server

    Ohtsubo, Junji

    2013-01-01

    This third edition of “Semiconductor Lasers, Stability, Instability and Chaos” was significantly extended.  In the previous edition, the dynamics and characteristics of chaos in semiconductor lasers after the introduction of the fundamental theory of laser chaos and chaotic dynamics induced by self-optical feedback and optical injection was discussed. Semiconductor lasers with new device structures, such as vertical-cavity surface-emitting lasers and broad-area semiconductor lasers, are interesting devices from the viewpoint of chaotic dynamics since they essentially involve chaotic dynamics even in their free-running oscillations. These topics are also treated with respect to the new developments in the current edition. Also the control of such instabilities and chaos control are critical issues for applications. Another interesting and important issue of semiconductor laser chaos in this third edition is chaos synchronization between two lasers and the application to optical secure communication. One o...

  17. Mining-caused changes to habitat structure affect amphibian and reptile population ecology more than metal pollution.

    Science.gov (United States)

    Sasaki, Kiyoshi; Lesbarrères, David; Watson, Glen; Litzgus, Jacqueline

    2015-12-01

    Emissions from smelting not only contaminate water and soil with metals, but also induce extensive forest dieback and changes in resource availability and microclimate. The relative effects of such co-occurring stressors are often unknown, but this information is imperative in developing targeted restoration strategies. We assessed the role and relative effects of structural alterations of terrestrial habitat and metal pollution caused by century-long smelting operations on amphibian and reptile communities by collecting environmental and time- and area-standardized multivariate abundance data along three spatially replicated impact gradients. Overall, species richness, diversity, and abundance declined progressively with increasing levels of metals (As, Cu, and Ni) and soil temperature (T(s)) and decreasing canopy cover, amount of coarse woody debris (CWD), and relative humidity (RH). The composite habitat variable (which included canopy cover, CWD, T(s), and RH) was more strongly associated with most response metrics than the composite metal variable (As, Cu, and Ni), and canopy cover alone explained 19-74% of the variance. Moreover, species that use terrestrial habitat for specific behaviors (e.g., hibernation, dispersal), especially forest-dependent species, were more severely affected than largely aquatic species. These results suggest that structural alterations of terrestrial habitat and concomitant changes in the resource availability and microclimate have stronger effects than metal pollution per se. Furthermore, much of the variation in response metrics was explained by the joint action of several environmental variables, implying synergistic effects (e.g., exacerbation of metal toxicity by elevated temperatures in sites with reduced canopy cover). We thus argue that the restoration of terrestrial habitat conditions is a key to successful recovery of herpetofauna communities in smelting-altered landscapes.

  18. Probing the onset of structural instabilities as a tool for detection of staling of dairy milk: A permittivity and conductivity study

    Science.gov (United States)

    Madhurima, V.; Harindran, Aswini

    2018-05-01

    Dairy milk is a worldwide drink and a versatile raw material for food industries too. The major issue regarding dairy milk is their contamination by micro-organisms and subsequent spoiling. Pasteurization and sealed packing are used to minimize this contamination. The presence of pathogenic micro-organisms like psychrotrophs, reduces the pH of fresh milk by fermenting the lactose into lactic acid leading to the spoiling of milk. While there are various tests to check the spoilage of milk, there is no unique test to detect the onset of the complex dynamics of spoilage. There have been some studies on the dielectric properties of dairy milk but the primary method of identification of freshness of milk is through the measurement of pH. In this study, broadband dielectric spectroscopy is used as a tool to probe the spoiling of milk and that provides the information about the structural changes of milk during spoilage. The gamma dispersion explains the influence of free water content which is found to be a sensitive tool to probe the onset of milk spoilage process. The observations here are further backed by studies on the particle size and zeta potential.

  19. Size effects on cavitation instabilities

    DEFF Research Database (Denmark)

    Niordson, Christian Frithiof; Tvergaard, Viggo

    2006-01-01

    growth is here analyzed for such cases. A finite strain generalization of a higher order strain gradient plasticity theory is applied for a power-law hardening material, and the numerical analyses are carried out for an axisymmetric unit cell containing a spherical void. In the range of high stress...... 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...... as the void grows to a size well above the characteristic material length....

  20. Beam instability studies at the APS

    International Nuclear Information System (INIS)

    Teng, L.C.

    1994-01-01

    The Argonne Advanced Photon Source, APS (Fig. 1), is a 7-GeV positron storage ring with a circumference of 1104 m. It has a ''third generation, DBA or Chasman-Green'' lattice composed of 40 sectors each having a ∼6 m long zero-dispersion straight-section for accommodating insertion devices. Neighboring straight-sections are connected by a 360 degrees/40 = 9 degrees double-bend-achromatic bending section designed to produce the smallest emittance attainable with reasonable component parameter values and dynamic apertures. Thus, it is a very strongly focusing lattice with v x = 35.22 and v y = 14.30. The beam chamber of the storage ring including all rf, vacuum and photon beam components is designed to ensure that a beam current > 100 mA can be stably stored. We expect that the maximum stable beam current could be as high as 300 mA. This paper will give some details of the studies and computations to ensure the stability of such a beam. The discussions will be organized in the following three parts: Coupled-bunch instability caused by the higher-order modes (HOMs) of the rf cavities; Single-bunch instability due to the resistive wall impedance; and Single-bunch instability due to broadband impedances arising from beam chamber irregularities

  1. Feedback stabilization of electrostatic reactive instabilities

    International Nuclear Information System (INIS)

    Richards, R.K.

    1976-01-01

    A general theory for the feedback stabilization of electrostatic reactive instabilities is developed which includes the effects of dissipation in the plasma and frequency dependence in the sensor-suppressor elements and in the external feedback circuit. This theory is compared to experiments involving particular reactive instability, an interchange mode, found in a magnetic mirror device; these results are found to be in good agreement with theory. One noteworthy result is that a frequency dependence in the overall gain and phase shift of the feedback loop can cause destabilization at large gain. Multimode feedback stabilization is studied using the spatial variation of two interchange modes to separate them such that each can be acted upon individually by the feedback system. The transfer function of the plasma is also examined. This analysis is used for mode identification and location of the pole positions. As an example of using feedback as a diagnostic tool, instability induced transport is studied. Here feedback is used to control the amplitude of fluctuations at saturation

  2. Resistive instabilities in tokamaks

    International Nuclear Information System (INIS)

    Rutherford, P.H.

    1985-10-01

    Low-m tearing modes constitute the dominant instability problem in present-day tokamaks. In this lecture, the stability criteria for representative current profiles with q(0)-values slightly less than unit are reviewed; ''sawtooth'' reconnection to q(0)-values just at, or slightly exceeding, unity is generally destabilizing to the m = 2, n = 1 and m = 3, n = 2 modes, and severely limits the range of stable profile shapes. Feedback stabilization of m greater than or equal to 2 modes by rf heating or current drive, applied locally at the magnetic islands, appears feasible; feedback by island current drive is much more efficient, in terms of the radio-frequency power required, then feedback by island heating. Feedback stabilization of the m = 1 mode - although yielding particularly beneficial effects for resistive-tearing and high-beta stability by allowing q(0)-values substantially below unity - is more problematical, unless the m = 1 ideal-MHD mode can be made positively stable by strong triangular shaping of the central flux surfaces. Feedback techniques require a detectable, rotating MHD-like signal; the slowing of mode rotation - or the excitation of non-rotating modes - by an imperfectly conducting wall is also discussed

  3. The Rayleigh-Taylor instability in inertial fusion, astrophysical plasma and flames

    International Nuclear Information System (INIS)

    Bychkov, V; Modestov, M; Akkerman, V; Eriksson, L-E

    2007-01-01

    Previous results are reviewed and new results are presented on the Rayleigh-Taylor instability in inertial confined fusion, flames and supernovae including gravitational and thermonuclear explosion mechanisms. The instability couples micro-scale plasma effects to large-scale hydrodynamic phenomena. In inertial fusion the instability reduces target compression. In supernovae the instability produces large-scale convection, which determines the fate of the star. The instability is often accompanied by mass flux through the unstable interface, which may have either a stabilizing or a destabilizing influence. Destabilization happens due to the Darrieus-Landau instability of a deflagration front. Still, it is unclear whether the instabilities lead to well-organized large-scale structures (bubbles) or to relatively isotropic turbulence (mixing layer)

  4. Population structure and temporal maintenance of the multihost fungal pathogen Botrytis cinerea: causes and implications for disease management.

    Science.gov (United States)

    Walker, Anne-Sophie; Gladieux, Pierre; Decognet, Véronique; Fermaud, Marc; Confais, Johann; Roudet, Jean; Bardin, Marc; Bout, Alexandre; Nicot, Philippe C; Poncet, Christine; Fournier, Elisabeth

    2015-04-01

    Understanding the causes of population subdivision is of fundamental importance, as studying barriers to gene flow between populations may reveal key aspects of the process of adaptive divergence and, for pathogens, may help forecasting disease emergence and implementing sound management strategies. Here, we investigated population subdivision in the multihost fungus Botrytis cinerea based on comprehensive multiyear sampling on different hosts in three French regions. Analyses revealed a weak association between population structure and geography, but a clear differentiation according to the host plant of origin. This was consistent with adaptation to hosts, but the distribution of inferred genetic clusters and the frequency of admixed individuals indicated a lack of strict host specificity. Differentiation between individuals collected in the greenhouse (on Solanum) and outdoor (on Vitis and Rubus) was stronger than that observed between individuals from the two outdoor hosts, probably reflecting an additional isolating effect associated with the cropping system. Three genetic clusters coexisted on Vitis but did not persist over time. Linkage disequilibrium analysis indicated that outdoor populations were regularly recombining, whereas clonality was predominant in the greenhouse. Our findings open up new perspectives for disease control by managing plant debris in outdoor conditions and reinforcing prophylactic measures indoor. © 2014 Society for Applied Microbiology and John Wiley & Sons Ltd.

  5. Structure-based analysis of five novel disease-causing mutations in 21-hydroxylase-deficient patients.

    Directory of Open Access Journals (Sweden)

    Carolina Minutolo

    2011-01-01

    Full Text Available Congenital adrenal hyperplasia (CAH due to 21-hydroxylase deficiency is the most frequent inborn error of metabolism, and accounts for 90-95% of CAH cases. The affected enzyme, P450C21, is encoded by the CYP21A2 gene, located together with a 98% nucleotide sequence identity CYP21A1P pseudogene, on chromosome 6p21.3. Even though most patients carry CYP21A1P-derived mutations, an increasing number of novel and rare mutations in disease causing alleles were found in the last years. In the present work, we describe five CYP21A2 novel mutations, p.R132C, p.149C, p.M283V, p.E431K and a frameshift g.2511_2512delGG, in four non-classical and one salt wasting patients from Argentina. All novel point mutations are located in CYP21 protein residues that are conserved throughout mammalian species, and none of them were found in control individuals. The putative pathogenic mechanisms of the novel variants were analyzed in silico. A three-dimensional CYP21 structure was generated by homology modeling and the protein design algorithm FoldX was used to calculate changes in stability of CYP21A2 protein. Our analysis revealed changes in protein stability or in the surface charge of the mutant enzymes, which could be related to the clinical manifestation found in patients.

  6. How can we predict microstructural changes caused by the multiscale irradiation process occurred in materials having complicated and hierarchical structures?

    International Nuclear Information System (INIS)

    Morishita, Kazunori; Watanabe, Yoshiyuki; Yoshimatsu, Jun-ichi

    2008-01-01

    Challenging efforts are discussed to establish an advanced methodology for prediction of material's property and performance changes by irradiation, which will be necessary by all means for the advanced reactor maintenance technology in the future. The changes of material's properties and performance caused by irradiation, such as irradiation-induced hardening, ductility loss, and material's degradation leading to reduction in reactor lifetime, are primarily determined by microstructural changes in materials during irradiation, where athermal lattice defects are continuously produced by collisions between an irradiating particle and a target material atom, and subsequently the defects are aggregated via diffusion in the form of dislocation loops, voids, and solute precipitation. These radiation damage processes are in essence multiscale phenomena, which involve varying time- and length-scales, from ballistic binary collisions to collective atomic motion in the thermal spike stage followed by the thermal activation process. In this report, the multiscale modeling approach is proposed to understand the processes in materials having complicated and hierarchical structures. (author)

  7. Tunnelling instability via perturbation theory

    Energy Technology Data Exchange (ETDEWEB)

    Graffi, S. (Bologna Univ. (Italy). Dip. di Matematica); Grecchi, V. (Moderna Univ. (Italy). Dip. di Matematica); Jona-Lasinio, G. (Paris-11 Univ., 91 - Orsay (France). Lab. de Physique Theorique et Hautes Energies)

    1984-10-21

    The semiclassical limit of low lying states in a multiwell potential is studied by rigorous perturbative techniques. In particular tunnelling instability and localisation of wave functions is obtained in a simple way under small deformations of symmetric potentials.

  8. 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.

  9. 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...... exact instability solutions are complex to derive, not to mention the extra complexity introducing dimensional instability from the temperature gradients. Using an inverse variable substitution and comparing an exact theory with an analytical instability solution a method to design tie...

  10. Summary of longitudinal instabilities workshop

    Energy Technology Data Exchange (ETDEWEB)

    Chasman, R.

    1976-01-01

    A five-day ISABELLE workshop on longitudinal instabilities was held at Brookhaven, August 9-13, 1976. About a dozen outside accelerator experts, both from Europe and the U.S.A., joined the local staff for discussions of longitudinal instabilities in ISABELLE. An agenda of talks was scheduled for the first day of the workshop. Later during the week, a presentation was given on the subject ''A more rigorous treatment of Landau damping in longitudinal beam instabilities''. A few progress meetings were held in which disagreements regarding calculations of coupling impedances were clarified. A summary session was held on the last day. Heavy emphasis was put on single bunched beam instabilities in the microwave region extending above the cut-off frequency of the ISABELLE vacuum chamber.

  11. Predicting Catastrophic BGP Routing Instabilities

    National Research Council Canada - National Science Library

    Nguyen, Lien

    2004-01-01

    .... Currently, this critical function is performed by the Border Gateway Protocol (BGP) version 4 RF01771. Like all routing protocols, BGP is vulnerable to instabilities that reduce its effectiveness...

  12. Spatial and temporal instabilities in high voltage power devices

    Energy Technology Data Exchange (ETDEWEB)

    Milady, Saeed

    2010-01-29

    Dynamic avalanche can occur during the turn-off process of high voltage bipolar devices, e.g. IGBTs and p{sup +}n{sup -}n{sup +} power diodes, that may result in spatial instabilities of the homogeneous current density distribution across the device and the formation of current filaments. Filaments may cause the destruction of the device, mainly because of the high local temperatures. The first part of this work is dedicated to the current filament behavior. The positive feedback mechanisms caused by the transient current flow through the gate capacitance of an IGBT operating under short circuit conditions may result in oscillations and temporal instabilities of the IGBT current. The oscillations may cause electromagnetic interference (EMI). Furthermore, the positive feedback mechanism may accelerate the over-heating of the device and result in a thermal run-away. This is the subject of the second part of this work. In the first part of this work using the device simulation results of power diodes the underlying physical mechanisms of the filament dynamic is investigated. Simulation results of diode structures with evenly distributed doping inhomogeneities show that, the filament motion gets smoother as the distance between the inhomogeneities decreases. Hopping to faraway inhomogeneities turns into the hopping to neighboring ones and finally a smooth motion. In homogeneous structures the slow inhibitory effect of the electron-hole plasma extraction and the fast activation, due to hole current flowing along the filament, result in a smooth filament motion. An analytical model for the filament velocity under isothermal conditions is presented that can reproduce the simulation data satisfactorily. The influence of the boundary conditions on the filament behavior is discussed. The positive beveled edge termination prohibits a long stay of the filament at the edge reducing the risk of filament pinning. Self-heating effects may turn the initially electrically triggered

  13. Genomic instability and radiation effects

    International Nuclear Information System (INIS)

    Christian Streffer

    2007-01-01

    Complete text of publication follows. Cancer, genetic mutations and developmental abnormalities are apparently associated with an increased genomic instability. Such phenomena have been frequently shown in human cancer cells in vitro and in situ. It is also well-known that individuals with a genetic predisposition for cancer proneness, such as ataxia telangiectesia, Fanconi anaemia etc. demonstrate a general high genomic instability e.g. in peripheral lymphocytes before a cancer has developed. Analogous data have been found in mice which develop a specific congenital malformation which has a genetic background. Under these aspects it is of high interest that ionising radiation can increase the genomic instability of mammalian cells after exposures in vitro an in vivo. This phenomenon is expressed 20 to 40 cell cycles after the exposure e.g. by de novo chromosomal aberrations. Such effects have been observed with high and low LET radiation, high LET radiation is more efficient. With low LET radiation a good dose response is observed in the dose range 0.2 to 2.0 Gy, Recently it has been reported that senescence and genomic instability was induced in human fibroblasts after 1 mGy carbon ions (1 in 18 cells are hit), apparently bystander effects also occurred under these conditions. The instability has been shown with DNA damage, chromosomal aberrations, gene mutation and cell death. It is also transferred to the next generation of mice with respect to gene mutations, chromosomal aberrations and congenital malformations. Several mechanisms have been discussed. The involvement of telomeres has gained interest. Genomic instability seems to be induced by a general lesion to the whole genome. The transmission of one chromosome from an irradiated cell to an non-irradiated cell leads to genomic instability in the untreated cells. Genomic instability increases mutation rates in the affected cells in general. As radiation late effects (cancer, gene mutations and congenital

  14. Detecting instability in animal social networks: genetic fragmentation is associated with social instability in rhesus macaques.

    Directory of Open Access Journals (Sweden)

    Brianne A Beisner

    2011-01-01

    Full Text Available The persistence of biological systems requires evolved mechanisms which promote stability. Cohesive primate social groups are one example of stable biological systems, which persist in spite of regular conflict. We suggest that genetic relatedness and its associated kinship structure are a potential source of stability in primate social groups as kinship structure is an important organizing principle in many animal societies. We investigated the effect of average genetic relatedness per matrilineal family on the stability of matrilineal grooming and agonistic interactions in 48 matrilines from seven captive groups of rhesus macaques. Matrilines with low average genetic relatedness show increased family-level instability such as: more sub-grouping in their matrilineal groom network, more frequent fighting with kin, and higher rates of wounding. Family-level instability in multiple matrilines within a group is further associated with group-level instability such as increased wounding. Stability appears to arise from the presence of clear matrilineal structure in the rhesus macaque group hierarchy, which is derived from cohesion among kin in their affiliative and agonistic interactions with each other. We conclude that genetic relatedness and kinship structure are an important source of group stability in animal societies, particularly when dominance and/or affilative interactions are typically governed by kinship.

  15. Aerodynamic instability: A case history

    Science.gov (United States)

    Eisenmann, R. C.

    1985-01-01

    The identification, diagnosis, and final correction of complex machinery malfunctions typically require the correlation of many parameters such as mechanical construction, process influence, maintenance history, and vibration response characteristics. The progression is reviewed of field testing, diagnosis, and final correction of a specific machinery instability problem. The case history presented addresses a unique low frequency instability problem on a high pressure barrel compressor. The malfunction was eventually diagnosed as a fluidic mechanism that manifested as an aerodynamic disturbance to the rotor assembly.

  16. Surgical treatment of chest instability

    International Nuclear Information System (INIS)

    Kitka, M.; Masek, M.

    2015-01-01

    Fractures of the ribs is the most common thoracic injury after blunt trauma. Chest wall instability (flail chest) is a common occurrence in the presence of multiple ribs fracture. Unilateral or bilateral fractures more ribs anteriorly or posteriorly will produce enough instability that paradoxical respiratory motion results in hypoventilation of an unacceptable degree. Open approach and surgical stabilisation of the chest preserved pulmonary function, improved pain control, minimized posttraumatic deformities and shorter back to work time. (author)

  17. 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.

  18. 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....

  19. Waves and instabilities in plasmas

    International Nuclear Information System (INIS)

    Chen, L.

    1987-01-01

    The contents of this book are: Plasma as a Dielectric Medium; Nyquist Technique; Absolute and Convective Instabilities; Landau Damping and Phase Mixing; Particle Trapping and Breakdown of Linear Theory; Solution of Viasov Equation via Guilding-Center Transformation; Kinetic Theory of Magnetohydrodynamic Waves; Geometric Optics; Wave-Kinetic Equation; Cutoff and Resonance; Resonant Absorption; Mode Conversion; Gyrokinetic Equation; Drift Waves; Quasi-Linear Theory; Ponderomotive Force; Parametric Instabilities; Problem Sets for Homework, Midterm and Final Examinations

  20. Instability of enclosed horizons

    Science.gov (United States)

    Kay, Bernard S.

    2015-03-01

    We point out that there are solutions to the scalar wave equation on dimensional Minkowski space with finite energy tails which, if they reflect off a uniformly accelerated mirror due to (say) Dirichlet boundary conditions on it, develop an infinite stress-energy tensor on the mirror's Rindler horizon. We also show that, in the presence of an image mirror in the opposite Rindler wedge, suitable compactly supported arbitrarily small initial data on a suitable initial surface will develop an arbitrarily large stress-energy scalar near where the two horizons cross. Also, while there is a regular Hartle-Hawking-Israel-like state for the quantum theory between these two mirrors, there are coherent states built on it for which there are similar singularities in the expectation value of the renormalized stress-energy tensor. We conjecture that in other situations with analogous enclosed horizons such as a (maximally extended) Schwarzschild black hole in equilibrium in a (stationary spherical) box or the (maximally extended) Schwarzschild-AdS spacetime, there will be similar stress-energy singularities and almost-singularities—leading to instability of the horizons when gravity is switched on and matter and gravity perturbations are allowed for. All this suggests it is incorrect to picture a black hole in equilibrium in a box or a Schwarzschild-AdS black hole as extending beyond the past and future horizons of a single Schwarzschild (/Schwarzschild-AdS) wedge. It would thus provide new evidence for 't Hooft's brick wall model while seeming to invalidate the picture in Maldacena's ` Eternal black holes in AdS'. It would thereby also support the validity of the author's matter-gravity entanglement hypothesis and of the paper ` Brick walls and AdS/CFT' by the author and Ortíz.

  1. 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.

  2. Ionospheric modification and parametric instabilities

    International Nuclear Information System (INIS)

    Fejer, J.A.

    1979-01-01

    Thresholds and linear growth rates for stimulated Brillouin and Raman scattering and for the parametric decay instability are derived by using arguments of energy transfer. For this purpose an expression for the ponderomotive force is derived. Conditions under which the partial pressure force due to differential dissipation exceeds the ponderomotive force are also discussed. Stimulated Brillouin and Raman scattering are weakly excited by existing incoherent backscatter radars. The parametric decay instability is strongly excited in ionospheric heating experiments. Saturation theories of the parametric decay instability are therefore described. After a brief discussion of the purely growing instability the effect of using several pumps is discussed as well as the effects of inhomogenicity. Turning to detailed theories of ionospheric heating, artificial spread F is discussed in terms of a purely growing instability where the nonlinearity is due to dissipation. Field-aligned short-scale striations are explained in terms of dissipation of the parametrically excited Langmuir waves (plasma oscillations): they might be further amplified by an explosive instability (except the magnetic equator). Broadband absorption is probably responsible for the 'overshoot' effect: the initially observed level of parametrically excited Langmuir waves is much higher than the steady state level

  3. On the conventive instability evolution in a rotating gas disk

    International Nuclear Information System (INIS)

    Nikonov, S.V.; Solov'ev, L.S.

    1986-01-01

    The mechanism of formation of spiral configuration in a rotating gravitating gas disk, caused by the nonlinear development of the convective instability, is considered. The mechanism suggested may be considered as the model of formation of the galaxy spiral configuration in a rotating pregalactic gas disk due to the development of the convective instability. Unlike the popular at present conception of ''density waves'', formation of the spiral configuration, from this point of view, is the single process of the development of instability in the pregalactic gas cloud. The further advantageous star formation in the vicinity of the central region, in a strip and sleeves is caused by higher concentration of gas density and temperature in these regions

  4. 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.

  5. Study of physical, chemical and structural effects caused by ionizing radiation and preservation on human costal cartilage

    International Nuclear Information System (INIS)

    Martinho Junior, Antonio Carlos

    2008-01-01

    Tissue Banks around the world have stored human cartilages obtained from cadaver donors for use in several kinds of reconstructive surgeries. To ensure that such tissues are not contaminated, they have been sterilized with ionizing radiation. However, high doses of gamma radiation may cause undesirable changes in the tissues, decreasing the mechanical properties of the grafts. In this work, we evaluate physical/chemical and structural changes in deep-frozen (-70 deg C) or high concentration of glycerol (> 98%) preserved costal cartilage, before and after sterilization by ionizing radiation at 3 different doses (15, 25 and 50 kGy). Samples of human costal cartilage were obtained from 20 cadaver donors ranging between 18 and 55 years old. A 60 Co irradiator was used as irradiation source. Thermogravimetry (TG), Optical Coherence Tomography (OCT) and mechanical tension and compression tests were carried out to evaluate the changes in the cartilage. Regarding the thermogravimetric results, the obtained data has shown that the TG curves have the same pattern independently of the sample irradiated or not. On the other hand, non-irradiated samples showed great variability of thermogravimetric curves among different donors and for the same donor. Concerning the mechanical tests, when cartilages were irradiated with 15 kGy, their mechanical strength to tension was increased about 24%, in both deep-froze and preserved in glycerol samples. Samples deep-frozen, when irradiated with 25 and 50 kGy, presented a decrease of their mechanical behavior smaller than those preserved in high concentrations of glycerol and irradiated with the same dose. Therefore, deep-frozen cartilages can be sterilized with doses until 50 kGy and cartilages preserved in high concentrations of glycerol can be sterilized with doses until 25 kGy without significant changes in their bio-mechanical properties.(author)

  6. Identification and Quantification of Cause and Effects in Symbiosis of Corn with Arbuscular Mycorrehiza Fungus using Structural Equation Modeling Approach

    Directory of Open Access Journals (Sweden)

    M Jahan

    2015-09-01

    Full Text Available Considering to necessity and importance of determining mycorrhizal symbiosis level and its effects on crop agroecological characteristics as well as other related factors affecting this relationship, beside, the lack of an assured method for this purpose, the present study designed based on new perspectives and insights for determining cause and effects relations, latent variables using structural equation modeling (SEM approach. A field experiment was conducted during 2 years. A split plots arrangement based on randomized complete block design (RCBD with three replications was used. Treatments consisted four cropping systems (high, medium, and low input conventional as well as ecological system and four inoculations (mycorrhizae fungus: Glomus intraradices, plant growth promoting rhizobacteria (PGPR: (Azospirillum brasilense, Azotobacter paspali, dual inoculation: (fungus plus bacteria, and no-inoculation (control, which were allocated to main plots and sub plots, respectively. At the first step, a confirmatory factor analyzing was conducted resulted to two distinguished factors, and then the variables which had the most loads (weight on one of these two factors were determined. At the second step, considering ecophysiological basis of crops growth and development, in order to continue analyzing, the first factor (including: leaf area index (LAI, root length colonization percent (RLCP, dry matter (DM, stem diameter (D, SPAD readings and the second factor (including: maximum photosynthesis (Amax, specific root length (SRL, canopy temperature (CT, plant height (H, soil respiration rate (SRR, variable chlorophyll fluorescence to maximum chlorophyll fluorescence (Fv/Fm, plant tissue phosphorus content (%P determined resource capture latent construct and resource utilization latent construct, respectively. Correlation coefficients, squared multiple correlation coefficients, covariance matrices, direct and indirect path coefficients were calculated

  7. Are transaction taxes a cause of financial instability?

    Science.gov (United States)

    Fontini, Fulvio; Sartori, Elena; Tolotti, Marco

    2016-05-01

    We analyze a stylized market where N boundedly rational agents may decide to trade or not a share of a risky asset at subsequent trading dates. Agents' payoff depends on returns, which are endogenously determined taking into account observed and forecasted demand and an exogenous transaction tax. We study the time evolutions of demand, returns and market activity. We show that the introduction of a transaction tax generally helps in reducing variability of returns and market activity. On the other hand, there are market conditions under which a low taxation may lead the market into a very unstable phase characterized by the fluctuation of the fundamentals around two different regimes; indeed, under these circumstances, heteroscedasticity of time series is detected and statistically analyzed.

  8. Breast tumor copy number aberration phenotypes and genomic instability

    International Nuclear Information System (INIS)

    Fridlyand, Jane; Jain, Ajay N; McLennan, Jane; Ziegler, John; Chin, Koei; Devries, Sandy; Feiler, Heidi; Gray, Joe W; Waldman, Frederic; Pinkel, Daniel; Albertson, Donna G; Snijders, Antoine M; Ylstra, Bauke; Li, Hua; Olshen, Adam; Segraves, Richard; Dairkee, Shanaz; Tokuyasu, Taku; Ljung, Britt Marie

    2006-01-01

    Genomic DNA copy number aberrations are frequent in solid tumors, although the underlying causes of chromosomal instability in tumors remain obscure. Genes likely to have genomic instability phenotypes when mutated (e.g. those involved in mitosis, replication, repair, and telomeres) are rarely mutated in chromosomally unstable sporadic tumors, even though such mutations are associated with some heritable cancer prone syndromes. We applied array comparative genomic hybridization (CGH) to the analysis of breast tumors. The variation in the levels of genomic instability amongst tumors prompted us to investigate whether alterations in processes/genes involved in maintenance and/or manipulation of the genome were associated with particular types of genomic instability. We discriminated three breast tumor subtypes based on genomic DNA copy number alterations. The subtypes varied with respect to level of genomic instability. We find that shorter telomeres and altered telomere related gene expression are associated with amplification, implicating telomere attrition as a promoter of this type of aberration in breast cancer. On the other hand, the numbers of chromosomal alterations, particularly low level changes, are associated with altered expression of genes in other functional classes (mitosis, cell cycle, DNA replication and repair). Further, although loss of function instability phenotypes have been demonstrated for many of the genes in model systems, we observed enhanced expression of most genes in tumors, indicating that over expression, rather than deficiency underlies instability. Many of the genes associated with higher frequency of copy number aberrations are direct targets of E2F, supporting the hypothesis that deregulation of the Rb pathway is a major contributor to chromosomal instability in breast tumors. These observations are consistent with failure to find mutations in sporadic tumors in genes that have roles in maintenance or manipulation of the genome

  9. Collisionless Kelvin-Helmholtz instability and vortex-induced reconnection in the external region of the Earth magnetotail

    International Nuclear Information System (INIS)

    Pegoraro, F; Faganello, M; Califano, F

    2008-01-01

    In a magnetized plasma streaming with a non uniform velocity, the Kelvin-Helmholtz instability plays a major role in mixing different plasma regions and in stretching the magnetic field lines leading to the formation of layers with a sheared magnetic field where magnetic field line reconnection can take place. A relevant example is provided by the formation of a mixing layer between the Earth's magnetosphere and the solar wind at low latitudes during northward periods. In the considered configuration, in the presence of a magnetic field nearly perpendicular to the plane defined by the velocity field and its inhomogeneity direction, velocity shear drives a Kelvin-Helmholtz instability which advects and distorts the magnetic field configuration. If the Alfven velocity associated to the in-plane magnetic field is sufficiently weak with respect to the variation of the fluid velocity in the plasma, the Kelvin-Helmholtz instability generates fully rolled-up vortices which advect the magnetic field lines into a complex configuration, causing the formation of current layers along the inversion curves of the in-plane magnetic field component. Pairing of the vortices generated by the Kelvin-Helmholtz instability is a well know phenomenon in two-dimensional hydrodynamics. Here we investigate the development of magnetic reconnection during the vortex pairing process and show that completely different magnetic structures are produced depending on how fast the reconnection process develops on the time scale set by the pairing process.

  10. Vaccine instability in the cold chain: mechanisms, analysis and formulation strategies.

    Science.gov (United States)

    Kumru, Ozan S; Joshi, Sangeeta B; Smith, Dawn E; Middaugh, C Russell; Prusik, Ted; Volkin, David B

    2014-09-01

    Instability of vaccines often emerges as a key challenge during clinical development (lab to clinic) as well as commercial distribution (factory to patient). To yield stable, efficacious vaccine dosage forms for human use, successful formulation strategies must address a combination of interrelated topics including stabilization of antigens, selection of appropriate adjuvants, and development of stability-indicating analytical methods. This review covers key concepts in understanding the causes and mechanisms of vaccine instability including (1) the complex and delicate nature of antigen structures (e.g., viruses, proteins, carbohydrates, protein-carbohydrate conjugates, etc.), (2) use of adjuvants to further enhance immune responses, (3) development of physicochemical and biological assays to assess vaccine integrity and potency, and (4) stabilization strategies to protect vaccine antigens and adjuvants (and their interactions) during storage. Despite these challenges, vaccines can usually be sufficiently stabilized for use as medicines through a combination of formulation approaches combined with maintenance of an efficient cold chain (manufacturing, distribution, storage and administration). Several illustrative case studies are described regarding mechanisms of vaccine instability along with formulation approaches for stabilization within the vaccine cold chain. These include live, attenuated (measles, polio) and inactivated (influenza, polio) viral vaccines as well as recombinant protein (hepatitis B) vaccines. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

  11. Architectures and Algorithms for Control and Diagnostics of Coupled-Bunch Instabilities in Circular Accelerators

    Energy Technology Data Exchange (ETDEWEB)

    Teytelman, Dmitry

    2003-07-08

    Modern light sources and circular colliders employ large numbers of high-intensity particle bunches in order to achieve high luminosity. The electromagnetic coupling of bunches via resonant structures causes coherent instabilities at high beam currents. Achieving high luminosity requires the control of such unstable motion. Feedback control is challenging due to wideband nature of the problem with up to 250 MHz bandwidths required. This thesis presents digital signal processing architectures and diagnostic techniques for control of longitudinal and transverse coupled-bunch instabilities. Diagnostic capabilities integrated into the feedback system allow one to perform fast transient measurements of unstable dynamics by perturbing the beam from the controlled state via feedback and recording the time-domain response. Such measurements enable one to thoroughly characterize plant (beam) dynamics as well as performance of the feedback system. Beam dynamics can change significantly over the operating range of accelerator currents and energies . Here we present several methods for design of robust stabilizing feedback controllers. Experimental results from several accelerators are presented. A new baseband architecture for transverse feedback is described that compactly implements the digital processing functions using field-programmable gate array devices. The architecture is designed to be software configurable so that the same hardware can be used for instability control in different accelerators.

  12. Architectures and Algorithms for Control and Diagnostics of Coupled-Bunch Instabilities in Circular Accelerators

    International Nuclear Information System (INIS)

    Teytelman, Dmitry

    2003-01-01

    Modern light sources and circular colliders employ large numbers of high-intensity particle bunches in order to achieve high luminosity. The electromagnetic coupling of bunches via resonant structures causes coherent instabilities at high beam currents. Achieving high luminosity requires the control of such unstable motion. Feedback control is challenging due to wideband nature of the problem with up to 250 MHz bandwidths required. This thesis presents digital signal processing architectures and diagnostic techniques for control of longitudinal and transverse coupled-bunch instabilities. Diagnostic capabilities integrated into the feedback system allow one to perform fast transient measurements of unstable dynamics by perturbing the beam from the controlled state via feedback and recording the time-domain response. Such measurements enable one to thoroughly characterize plant (beam) dynamics as well as performance of the feedback system. Beam dynamics can change significantly over the operating range of accelerator currents and energies . Here we present several methods for design of robust stabilizing feedback controllers. Experimental results from several accelerators are presented. A new baseband architecture for transverse feedback is described that compactly implements the digital processing functions using field-programmable gate array devices. The architecture is designed to be software configurable so that the same hardware can be used for instability control in different accelerators

  13. Patellofemoral instability in children: T2 relaxation times of the patellar cartilage in patients with and without patellofemoral instability and correlation with morphological grading of cartilage damage.

    Science.gov (United States)

    Kang, Chang Ho; Kim, Hee Kyung; Shiraj, Sahar; Anton, Christopher; Kim, Dong Hoon; Horn, Paul S

    2016-07-01

    Patellofemoral instability is one of the most common causes of cartilage damage in teenagers. To quantitatively evaluate the patellar cartilage in patients with patellofemoral instability using T2 relaxation time maps (T2 maps), compare the values to those in patients without patellofemoral instability and correlate them with morphological grades in patients with patellofemoral instability. Fifty-three patients with patellofemoral instability (mean age: 15.9 ± 2.4 years) and 53 age- and gender-matched patients without patellofemoral instability were included. Knee MR with axial T2 map was performed. Mean T2 relaxation times were obtained at the medial, central and lateral zones of the patellar cartilage and compared between the two groups. In the patellofemoral instability group, morphological grading of the patellar cartilage (0-4) was performed and correlated with T2 relaxation times. Mean T2 relaxation times were significantly longer in the group with patellofemoral instability as compared to those of the control group across the patellar cartilage (Student's t-test, Ppatellofemoral instability, patellar cartilage damage occurs across the entire cartilage with the highest T2 values at the apex. T2 relaxation times directly reflect the severity in low-grade cartilage damage, which implies an important role for T2 maps in differentiating between normal and low-grade cartilage damage.

  14. Relación de la inestabilidad estructural con el manejo y propiedades de los suelos de la región pampeana Relation of structural instability with management and properties of soils in the Pampean region

    Directory of Open Access Journals (Sweden)

    Carina Rosa Álvarez

    2012-12-01

    Full Text Available La inestabilidad estructural (IEST permite caracterizar la resistencia a la degradación de los suelos. Se determinó la IEST (De Leenheer& De Boodt en 67 sitios de muestreo bajo distintos manejos en la Región Pampeana norte, con el objetivo de comparar los manejos y analizar su relación con: a la densidad aparente (DAP; b el contenido de carbono orgánico total y sus fracciones particulada (> 53 mm y resistente (Soil structural instability (IEST characterizes the resistance to degradation of soils. Soil IEST (De Leenheer and De Boodt was determined in 67 sites under different soil managements in the Northern Pampean Region, in order to establish its relation with: a core bulk density (DAP; b total organic carbon and its particulate (> 53 mm and resistant (<53 mm fractions; c granulometric fractions; and d relative compaction (ratio bulk density to maximum bulk density by Proctor Test. Soil IEST allowed distinguishing among quasi-pristine and agriculture under tillage (P<0.05. Meanwhile integrated crop-livestock systems under no tillage and agriculture under no tillage presented intermediate values. DAP was highest in the integrated crop-livestock systems under no tillage. A multiple regression model (R2 = 0.37 was fitted between IEST and total organic carbon and silt content and a Dummy variable related to management. DAP was negatively related with total organic carbon and clay content and positive with a Dummy variable (value= 1 for integrated crop-livestock systems and 0 for the others (R2= 0.62. Results suggest other stabilizing agents like the action of plant roots could be responsible for the variation in SI in these soils. It can be concluded that higher carbon contents are required to stabilize silty soils.

  15. Profiles of Genomic Instability in High-Grade Serous Ovarian Cancer Predict Treatment Outcome

    DEFF Research Database (Denmark)

    Wang, Zhigang C.; Birkbak, Nicolai Juul; Culhane, Aedín C.

    2012-01-01

    Purpose: High-grade serous cancer (HGSC) is the most common cancer of the ovary and is characterized by chromosomal instability. Defects in homologous recombination repair (HRR) are associated with genomic instability in HGSC, and are exploited by therapy targeting DNA repair. Defective HRR cause...

  16. Structural Instability in Ice VIII under Pressure

    International Nuclear Information System (INIS)

    Besson, J.; Klotz, S.; Hamel, G.; Marshall, W.; Nelmes, R.; Loveday, J.

    1997-01-01

    Below 125K, tetragonal ice VIII remains in a metastable form at ambient pressure. This form has long been considered to be identical to ice VIII, although unexplained discrepancies exist between their vibrational spectra. Neutron diffraction studies reveal an isostructural phase transformation below 2GPa related to a weakening of the bonds between the two D 2 O sublattices of ice VIII. In this new phase, ice VIII ' , the tetragonal distortion is 20% larger than in ice VIII, which accounts for the differences between the vibrational frequencies of the two phases. copyright 1997 The American Physical Society

  17. Conservation laws in baroclinic inertial-symmetric instabilities

    Science.gov (United States)

    Grisouard, Nicolas; Fox, Morgan B.; Nijjer, Japinder

    2017-04-01

    Submesoscale oceanic density fronts are structures in geostrophic and hydrostatic balance, but are more prone to instabilities than mesoscale flows. As a consequence, they are believed to play a large role in air-sea exchanges, near-surface turbulence and dissipation of kinetic energy of geostrophically and hydrostatically balanced flows. We will present two-dimensional (x, z) Boussinesq numerical experiments of submesoscale baroclinic fronts on the f-plane. Instabilities of the mixed inertial and symmetric types (the actual name varies across the literature) develop, with the absence of along-front variations prohibiting geostrophic baroclinic instabilities. Two new salient facts emerge. First, contrary to pure inertial and/or pure symmetric instability, the potential energy budget is affected, the mixed instability extracting significant available potential energy from the front and dissipating it locally. Second, in the submesoscale regime, the growth rate of this mixed instability is sufficiently large that significant radiation of near-inertial internal waves occurs. Although energetically small compared to e.g. local dissipation within the front, this process might be a significant source of near-inertial energy in the ocean.

  18. Instabilities in a nonstationary model of self-gravitating disks. III. The phenomenon of lopsidedness and a comparison of perturbation modes

    Science.gov (United States)

    Mirtadjieva, K. T.; Nuritdinov, S. N.; Ruzibaev, J. K.; Khalid, Muhammad

    2011-06-01

    This is an examination of the gravitational instability of the major large-scale perturbation modes for a fixed value of the azimuthal wave number m = 1 in nonlinearly nonstationary disk models with isotropic and anisotropic velocity diagrams for the purpose of explaining the displacement of the nucleus away from the geometric center (lopsidedness) in spiral galaxies. Nonstationary analogs of the dispersion relations for these perturbation modes are obtained. Critical diagrams of the initial virial ratio are constructed from the rotation parameters for the models in each case. A comparative analysis is made of the instability growth rates for the major horizontal perturbation modes in terms of two models, and it is found that, on the average, the instability growth rate for the m = 1 mode with a radial wave number N = 3 almost always has a clear advantage relative to the other modes. An analysis of these results shows that if the initial total kinetic energy in an isotropic model is no more than 12.4% of the initial potential energy, then, regardless of the value of the rotation parameter Ω, an instability of the radial motions always occurs and causes the nucleus to shift away from the geometrical center. This instability is aperiodic when Ω = 0 and is oscillatory when Ω ≠ 0 . For the anisotropic model, this kind of structure involving the nucleus develops when the initial total kinetic energy in the model is no more than 30.6% of the initial potential energy.

  19. Dynamic feedback for multi-mode plasma instabilities

    International Nuclear Information System (INIS)

    Sen, A.K.

    1978-01-01

    Constant feedback, which has been used exclusively, fails to stabilize more than one mode of a plasma instability. It is shown that a suitable dynamic or frequency-dependent feedback can stabilize all modes. Methods are developed in which such a feedback structure can be chosen in terms of its poles and zeros in relation to those of the plasma transfer function in the complex frequency plane. The synthesis procedure for such a feedback structure, in the form of an integrated electronic circuit is also discussed. As an example, a dynamic feedback for multi-mode stabilization of a collisional drift wave instability is developed in detail. (author)

  20. Rayleigh-Taylor instability in inertial confinement fusion

    International Nuclear Information System (INIS)

    Gupta, N.K.

    1987-01-01

    This report summarises the main results of theoretical analysis on the problem of Rayleigh-Tylor instability in inertial confinement fusion (ICF). Work presented in this report essentially covers four basic problems. Firstly, an analytical formulation to analyse the effects of plasma density inhomogeneities on the growth of the instability in plane geometry is presented. As a result of this analysis it is concluded that, for minimizing the growth rate of the instability, it may be advantageous to use the driver laser beams of higher irradiance and an optimum wave length in an ICF experiment. Secondly, a new formulation for the analysis of the instability in curved (cylindrical and spherical) geometries is presented. A general eigenvalue equation for the growth rate of the instability which is applicable for both plane and curved geometries is derived. A comparative study is made between the plane, cylindrical and spherical geometries. Also analytical expressions for the growth rates are obtained in the cases of spherical and cylindrical shell targets and their variations with respect to the aspect ratios of the shells are discussed. Thirdly, a semi-analytical analysis of the instability where the growth rate is obtained by solving numerically a (2N-1)x(2N-1) determinantal equation is presented. The semi-analytical analysis developed is applicable for the study of the growth of the instability in the present day multi-structured spherical shell targets. Finally, a dynamic analysis of the growth of the instability for a representative spherical solid target driven by laser beams symmetrically from all the sides is carried out numerically using a computer code developed for this purpose. This study confirms analytical predictions. Further, it is observed that an approximate analytical analysis with time independent density profile gives conservative estimates for the growth rate. In passing, the computer code is also used to estimate the pellet gain for spin