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Sample records for stage magnetic rayleigh-taylor

  1. Rayleigh-Taylor instabilities with sheared magnetic fields

    International Nuclear Information System (INIS)

    Ruderman, M. S.; Terradas, J.; Ballester, J. L.

    2014-01-01

    Magnetic Rayleigh-Taylor (MRT) instabilities may play a relevant role in many astrophysical problems. In this work the effect of magnetic shear on the growth rate of the MRT instability is investigated. The eigenmodes of an interface and a slab model under the presence of gravity are analytically calculated assuming that the orientation of the magnetic field changes in the equilibrium, i.e., there is magnetic shear. We solve the linearized magnetohydrodynamic equations in the incompressible regime. We find that the growth rate is bounded under the presence of magnetic shear. We have derived simple analytical expressions for the maximum growth rate, corresponding to the most unstable mode of the system. These expressions provide the explicit dependence of the growth rate on the various equilibrium parameters. For small angles the growth time is linearly proportional to the shear angle, and in this regime the single interface problem and the slab problem tend to the same result. On the contrary, in the limit of large angles and for the interface problem the growth time is essentially independent of the shear angle. In this regime we have also been able to calculate an approximate expression for the growth time for the slab configuration. Magnetic shear can have a strong effect on the growth rates of the instability. As an application of the results found in this paper we have indirectly determined the shear angle in solar prominence threads using their lifetimes and the estimation of the Alfvén speed of the structure.

  2. Rayleigh-Taylor instabilities with sheared magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    Ruderman, M. S. [Solar Physics and Space Plasma Research Centre (SP2RC), University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Terradas, J.; Ballester, J. L. [Departament de Física, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2014-04-20

    Magnetic Rayleigh-Taylor (MRT) instabilities may play a relevant role in many astrophysical problems. In this work the effect of magnetic shear on the growth rate of the MRT instability is investigated. The eigenmodes of an interface and a slab model under the presence of gravity are analytically calculated assuming that the orientation of the magnetic field changes in the equilibrium, i.e., there is magnetic shear. We solve the linearized magnetohydrodynamic equations in the incompressible regime. We find that the growth rate is bounded under the presence of magnetic shear. We have derived simple analytical expressions for the maximum growth rate, corresponding to the most unstable mode of the system. These expressions provide the explicit dependence of the growth rate on the various equilibrium parameters. For small angles the growth time is linearly proportional to the shear angle, and in this regime the single interface problem and the slab problem tend to the same result. On the contrary, in the limit of large angles and for the interface problem the growth time is essentially independent of the shear angle. In this regime we have also been able to calculate an approximate expression for the growth time for the slab configuration. Magnetic shear can have a strong effect on the growth rates of the instability. As an application of the results found in this paper we have indirectly determined the shear angle in solar prominence threads using their lifetimes and the estimation of the Alfvén speed of the structure.

  3. Magnetic Rayleigh-Taylor Instability in Radiative Flows

    Science.gov (United States)

    Yaghoobi, Asiyeh; Shadmehri, Mohsen

    2018-03-01

    We present a linear analysis of the radiative Rayleigh-Taylor (RT) instability in the presence of magnetic field for both optically thin and thick regimes. When the flow is optically thin, magnetic field not only stabilizes perturbations with short wavelengths, but also growth rate of the instability at long wavelengths is reduced compared to a nonmagnetized case. Then, we extend our analysis to the optically thick flows with a conserved total specific entropy and properties of the unstable perturbations are investigated in detail. Growth rate of the instability at short wavelengths is suppressed due to the presence of the magnetic field, however, growth rate is nearly constant at long wavelengths because of the radiation field. Since the radiative bubbles around massive protostars are subject to the RT instability, we also explore implications of our results in this context. In the nonmagnetized case, the growth time-scale of the instability for a typical bubble is found less than one thousand years which is very short compared to the typical star formation time-scale. Magnetic field with a reasonable strength significantly increases the growth time-scale to more than hundreds of thousands years. The instability, furthermore, is more efficient at large wavelengths, whereas in the non-magnetized case, growth rate at short wavelengths is more significant.

  4. Effect of magnetic field on Rayleigh-Taylor instability of two superposed fluids

    International Nuclear Information System (INIS)

    Sharma, P K; Tiwari, Anita; Chhajlani, R K

    2012-01-01

    The effect of two dimensional magnetic field on the Rayleigh-Taylor (R-T) instability in an incompressible plasma is investigated to include simultaneously the effects of suspended particles and the porosity of the medium. The relevant linearized perturbation equations have been solved. The explicit expression of the linear growth rate is obtained in the presence of fixed boundary conditions. A stability criterion for the medium is derived and discussed the Rayleigh Taylor instabilities in different configurations. It is found that the basic Rayleigh-Taylor instability condition is modified by the presence of magnetic field, suspended particles and porosity of the medium. In case of an unstable R-T configuration, the magnetic field has a stabilizing effect on the system. It is also found that the growth rate of an unstable R-T mode decreases with increasing relaxation frequency thereby showing a stabilizing influence on the R-T configuration.

  5. Rayleigh-Taylor-instability evolution in colliding-plasma-jet experiments with magnetic and viscous stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Adams, Colin Stuart [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of New Mexico, Albuquerque, NM (United States); Univ. of Washington, Seattle, WA (United States)

    2015-01-15

    The Rayleigh-Taylor instability causes mixing in plasmas throughout the universe, from micron-scale plasmas in inertial confinement fusion implosions to parsec-scale supernova remnants. The evolution of this interchange instability in a plasma is influenced by the presence of viscosity and magnetic fields, both of which have the potential to stabilize short-wavelength modes. Very few experimental observations of Rayleigh-Taylor growth in plasmas with stabilizing mechanisms are reported in the literature, and those that are reported are in sub-millimeter scale plasmas that are difficult to diagnose. Experimental observations in well-characterized plasmas are important for validation of computational models used to make design predictions for inertial confinement fusion efforts. This dissertation presents observations of instability growth during the interaction between a high Mach-number, initially un-magnetized plasma jet and a stagnated, magnetized plasma. A multi-frame fast camera captures Rayleigh-Taylor-instability growth while interferometry, spectroscopy, photodiode, and magnetic probe diagnostics are employed to estimate plasma parameters in the vicinity of the collision. As the instability grows, an evolution to longer mode wavelength is observed. Comparisons of experimental data with idealized magnetohydrodynamic simulations including a physical viscosity model suggest that the observed instability evolution is consistent with both magnetic and viscous stabilization. These data provide the opportunity to benchmark computational models used in astrophysics and fusion research.

  6. Theoretical and numerical study of Rayleigh-Taylor instabilities in magnetized plasmas; Etude theorique et numerique des instabilites rayleigh-taylor en plasmas magnetises

    Energy Technology Data Exchange (ETDEWEB)

    Andrei, A. Ivanov

    2001-06-15

    In this thesis we're studying both the general case of the 'classic' Rayleigh-Taylor instability (in incompressible fluids) and more specific cases of the instabilities of Rayleigh-Taylor type in magnetized plasmas, in the liners or wire array implosions etc. We have studied the influence of the Hall diffusion of magnetic field on the growth rate of the instability. We have obtained in this work a self-similar solution for the widening of the initial profile of the magnetic field and for the wave of the penetration of magnetic field. After that the subsequent evolution of the magnetic field in plasma opening switches (POS) has been examined. We have shown the possibility of the existence of a strong rarefaction wave for collisional and non-collisional cases. This wave can explain the phenomenon of the opening of POS. The effect of the suppression of Rayleigh-Taylor instability by forced oscillations of the boundary between two fluids permits us to propose some ideas for the experiments of inertial fusion. We have considered the general case of the instability, in other words - two incompressible viscous superposed fluids in a gravitational field. We have obtained an exact analytical expression for the growth rate and then we have analyzed the influence of the parameters of external 'pumping' on the instability. These results can be applied to a wide range of systems, starting from classic hydrodynamics and up to astrophysical plasmas. The scheme of wire arrays has become recently a very popular method to obtain a high power X-radiation or for a high quality implosion in Z-pinches. The experimental studies have demonstrated that the results of implosion are much better for the case of multiple thin wires situated cylindrically than in a usual liner scheme. We have examined the problem modeling the stabilization of Rayleigh-Taylor instability for a wire array system. The reason for instability suppression is the regular spatial modulation of

  7. Magnetic field generation in Rayleigh-Taylor unstable inertial confinement fusion plasmas.

    Science.gov (United States)

    Srinivasan, Bhuvana; Dimonte, Guy; Tang, Xian-Zhu

    2012-04-20

    Rayleigh-Taylor instabilities (RTI) in inertial confinement fusion implosions are expected to generate magnetic fields. A Hall-MHD model is used to study the field generation by 2D single-mode and multimode RTI in a stratified two-fluid plasma. Self-generated magnetic fields are predicted and these fields grow as the RTI progresses via the ∇n(e)×∇T(e) term in the generalized Ohm's law. Scaling studies are performed to determine the growth of the self-generated magnetic field as a function of density, acceleration, Atwood number, and perturbation wavelength.

  8. Theoretical and numerical study of Rayleigh-Taylor instabilities in magnetized plasmas

    International Nuclear Information System (INIS)

    Andrei, A. Ivanov

    2001-06-01

    In this thesis we're studying both the general case of the 'classic' Rayleigh-Taylor instability (in incompressible fluids) and more specific cases of the instabilities of Rayleigh-Taylor type in magnetized plasmas, in the liners or wire array implosions etc. We have studied the influence of the Hall diffusion of magnetic field on the growth rate of the instability. We have obtained in this work a self-similar solution for the widening of the initial profile of the magnetic field and for the wave of the penetration of magnetic field. After that the subsequent evolution of the magnetic field in plasma opening switches (POS) has been examined. We have shown the possibility of the existence of a strong rarefaction wave for collisional and non-collisional cases. This wave can explain the phenomenon of the opening of POS. The effect of the suppression of Rayleigh-Taylor instability by forced oscillations of the boundary between two fluids permits us to propose some ideas for the experiments of inertial fusion. We have considered the general case of the instability, in other words - two incompressible viscous superposed fluids in a gravitational field. We have obtained an exact analytical expression for the growth rate and then we have analyzed the influence of the parameters of external 'pumping' on the instability. These results can be applied to a wide range of systems, starting from classic hydrodynamics and up to astrophysical plasmas. The scheme of wire arrays has become recently a very popular method to obtain a high power X-radiation or for a high quality implosion in Z-pinches. The experimental studies have demonstrated that the results of implosion are much better for the case of multiple thin wires situated cylindrically than in a usual liner scheme. We have examined the problem modeling the stabilization of Rayleigh-Taylor instability for a wire array system. The reason for instability suppression is the regular spatial modulation of the surface plasma-magnetic

  9. Effect of magnetic field on Rayleigh-Taylor instability of quantum and stratified plasma in porous medium

    International Nuclear Information System (INIS)

    Sharma, P.K.; Tiwari, Anita; Argal, Shraddha; Chhajlani, R.K.

    2013-01-01

    This paper is devoted to an investigation of Quantum effects and magnetic field effects on the Rayleigh Taylor instability of two superposed incompressible fluids in bounded porous medium. The Quantum magneto hydrodynamic equations are solved by using normal mode method and a dispersion relation is obtained. The dispersion relation is derived for the case where plasma is bounded by two rigid planes z = 0 and z = h. The Rayleigh Taylor instability growth rate and stability condition of the medium is discussed in the presence of quantum effect, magnetic field, porosity and permeability. It is found that the magnetic field and medium porosity have stabilizing influence while permeability has destabilizing influence on the Rayleigh Taylor instability. (author)

  10. Development of Richtmyer-Meshkov and Rayleigh-Taylor instability in the presence of magnetic field

    International Nuclear Information System (INIS)

    Khan, Manoranjan; Mandal, Labakanta; Banerjee, Rahul; Roy, Sourav; Gupta, M.R.

    2011-01-01

    Fluid instabilities like Rayleigh-Taylor (R-T), Richtmyer-Meshkov (R-M) and Kelvin-Helmholtz (K-H) instability can occur in a wide range of physical phenomenon from astrophysical context to Inertial Confinement Fusion (ICF). Using Layzer's potential flow model, we derive the analytical expressions of growth rate of bubble and spike for ideal magnetized fluid in R-T and R-M cases. In the presence of transverse magnetic field, the R-M and R-T instabilities are suppressed or enhanced depending on the direction of magnetic pressure and hydrodynamic pressure. Again the interface of two fluid may oscillate if both the fluids are conducting. However, it is observed that the magnetic field has no effect in linear case.

  11. Compressibility Effect on the Rayleigh-Taylor Instability with Sheared Magnetic Fields

    Science.gov (United States)

    Ruderman, M. S.

    2017-04-01

    We study the effect of plasma compressibility on the Rayleigh-Taylor instability of a magnetic interface with a sheared magnetic field. We assume that the plasma is ideal and the equilibrium quantities are constant above and below the interface. We derive the dispersion equation. Written in dimensionless variables, it contains seven dimensionless parameters: the ratio of plasma densities above and below the interface ζ, the ratio of magnetic field magnitude squared χ, the shear angle α, the plasma beta above and below the interface, β2 and β1, the angle between the perturbation wave number and the magnetic field direction above the interface φ, and the dimensionless wave number κ. Only six of these parameters are independent because χ, β1, and β2 are related by the condition of total pressure continuity at the interface. Only perturbations with the wave number smaller than the critical wave number are unstable. The critical wave number depends on φ, but it is independent of β1 and β2, and is the same as that in the incompressible plasma approximation. The dispersion equation is solved numerically with ζ= 100, χ= 1, and β1 = β2 = β. We obtain the following results. When β decreases, so does the maximum instability increment. However, the effect is very moderate. It is more pronounced for high values of α. We also calculate the dependence on φ of the maximum instability increment with respect to κ. The instability increment takes its maximum at φ= φm. Again, the decrease of β results in the reduction of the instability increment. This reduction is more pronounced for high values of |φ- φm|. When both α and |φ- φm| are small, the reduction effect is practically negligible. The theoretical results are applied to the magnetic Rayleigh-Taylor instability of prominence threads in the solar atmosphere.

  12. Stabilization of Rayleigh-Taylor instability due to the spontaneous magnetic field in laser produced plasma

    International Nuclear Information System (INIS)

    Ogasawara, Masatada; Takita, Masami.

    1981-08-01

    Spontaneous magnetic fields due to the temperature gradient nabla T 0 produced by a focussed laser beam on one point of a pellet are taken into account in deriving the dispersion relation of Rayleigh-Taylor instability. Growth rate γ decreases with time. Density fluctuation with wavelength shorter than 1.5(R/L sub(T)) x (n sub(s)/n 0 )sup(1/2) μm is remarkably stabilized, where R, L sub(T), n sub(s) and n 0 are the radius of a pellet, L sub(T)sup(-1) = + nabla T 0 /T 0 + , number densities of solid and the pellet. Validity condition of the theory is γt 0 >> 1 or in another form R >> L, where t 0 is the time of thermal expansion of a pellet and L -1 = + nabla n 0 /n 0 + . (author)

  13. Single-Mode Deceleration Stage Rayleigh-Taylor Instability Growth in Cylindrical Implosions

    Science.gov (United States)

    Sauppe, J. P.; Palaniyappan, S.; Bradley, P. A.; Batha, S. H.; Loomis, E. N.; Kline, J. L.; Srinivasan, B.; Bose, A.; Malka, E.; Shvarts, D.

    2017-10-01

    We present design calculations demonstrating the feasibility of measuring single-mode deceleration stage Rayleigh-Taylor instability (RTI) growth at a factor of four convergence. RTI growth rates are modified as a result of convergence [Bell LA-1321, 1951], and cylindrical targets are considered here, as they allow direct diagnostic access along the interface. The 2D computations, performed with the radiation-hydrodynamics code xRAGE [Gittings et al., CSD 2008] utilizing a new laser ray-tracing package, predict growth factors of 6 to 10 for mode 10 and 4 to 6 for mode 4, both of high interest in evaluating inertial confinement fusion capsule degradation mechanisms [Bose et al., this conference]. These results compare favorably to a linear theory [Epstein, PoP 2004] and to a buoyancy-drag model [Srebro et al., LPB 2003], which accounts for the linear and non-linear stages. Synthetic radiographs, produced by combining 2D computations of axial and transverse cross-sections, indicate this growth will be observable, and these will be compared to experimental data obtained at the OMEGA laser facility. Work performed by Los Alamos National Laboratory under contract DE-AC52-06NA25396 for the National Nuclear Security Administration of the U.S. Department of Energy. (LA-UR-17-25608).

  14. Rayleigh Taylor instability of two superposed compressible fluids in un-magnetized plasma

    International Nuclear Information System (INIS)

    Sharma, P K; Tiwari, A; Argal, S; Chhajlani, R K

    2014-01-01

    The linear Rayleigh Taylor instability of two superposed compressible Newtonian fluids is discussed with the effect of surface tension which can play important roles in space plasma. As in both the superposed Newtonian fluids, the system is stable for potentially stable case and unstable for potentially unstable case in the present problem also. The equations of the problem are solved by normal mode method and a dispersion relation is obtained for such a system. The behaviour of growth rate is examined in the presence of surface tension and it is found that the surface tension has stabilizing influence on the Rayleigh Taylor instability of two superposed compressible fluids. Numerical analysis is performed to show the effect of sound velocity and surface tension on the growth rate of Rayleigh Taylor instability. It is found that both parameters have stabilizing influence on the growth rate of Rayleigh Taylor instability.

  15. Measurements of Rayleigh-Taylor-Induced Magnetic Fields in the Linear and Non-linear Regimes

    Science.gov (United States)

    Manuel, Mario

    2012-10-01

    Magnetic fields are generated in plasmas by the Biermann-battery, or thermoelectric, source driven by non-collinear temperature and density gradients. The ablation front in laser-irradiated targets is susceptible to Rayleigh-Taylor (RT) growth that produces gradients capable of generating magnetic fields. Measurements of these RT-induced magnetic fields in planar foils have been made using a combination of x-ray and monoenergetic-proton radiography techniques. At a perturbation wavelength of 120 μm, proton radiographs indicate an increase of the magnetic-field strength from ˜1 to ˜10 Tesla during the linear growth phase. A characteristic change in field structure was observed later in time for irradiated foils of different initial surface perturbations. Proton radiographs show a regular cellular configuration initiated at the same time during the drive, independent of the initial foil conditions. This non-linear behavior has been experimentally investigated and the source of these characteristic features will be discussed.

  16. The non-linear growth of the magnetic Rayleigh-Taylor instability

    Science.gov (United States)

    Carlyle, Jack; Hillier, Andrew

    2017-09-01

    This work examines the effect of the embedded magnetic field strength on the non-linear development of the magnetic Rayleigh-Taylor instability (RTI) (with a field-aligned interface) in an ideal gas close to the incompressible limit in three dimensions. Numerical experiments are conducted in a domain sufficiently large so as to allow the predicted critical modes to develop in a physically realistic manner. The ratio between gravity, which drives the instability in this case (as well as in several of the corresponding observations), and magnetic field strength is taken up to a ratio which accurately reflects that of observed astrophysical plasma, in order to allow comparison between the results of the simulations and the observational data which served as inspiration for this work. This study finds reduced non-linear growth of the rising bubbles of the RTI for stronger magnetic fields, and that this is directly due to the change in magnetic field strength, rather than the indirect effect of altering characteristic length scales with respect to domain size. By examining the growth of the falling spikes, the growth rate appears to be enhanced for the strongest magnetic field strengths, suggesting that rather than affecting the development of the system as a whole, increased magnetic field strengths in fact introduce an asymmetry to the system. Further investigation of this effect also revealed that the greater this asymmetry, the less efficiently the gravitational energy is released. By better understanding the under-studied regime of such a major phenomenon in astrophysics, deeper explanations for observations may be sought, and this work illustrates that the strength of magnetic fields in astrophysical plasmas influences observed RTI in subtle and complex ways.

  17. Nonlinear saturated states of the magnetic-curvature-driven Rayleigh-Taylor instability in three dimensions

    International Nuclear Information System (INIS)

    Das, Amita; Sen, Abhijit; Kaw, Predhiman; Benkadda, S.; Beyer, Peter

    2005-01-01

    Three-dimensional electromagnetic fluid simulations of the magnetic-curvature-driven Rayleigh-Taylor instability are presented. Issues related to the existence of nonlinear saturated states and the nature of the temporal evolution to such states from random initial conditions are addressed. It is found that nonlinear saturated states arising from generation of zonal shear flows continue to exist in certain parametric domains but their spectrum and spatial characteristics have important differences from earlier two-dimensional results reported in Phys. Plasmas 4, 1018 (1997) and Phys. Plasmas 8, 5104 (2001). In particular, the three-dimensional nonlinear states possess a significant power level in short scales and the spatial structures of the potential and density fluctuations appear not to develop any functional correlations. Electromagnetic effects are found to inhibit the formation of zonal flows and thereby to considerably restrict the parametric domain of nonlinear stabilization. The role of finite k parallel and the contribution of the unstable drift wave branch are also discussed and delineated through a number of simulation studies carried out in special simplified limits

  18. Hydromagnetic Rayleigh-Taylor instability of Oldroydian viscoelastic fluids in porous medium in presence of variable magnetic field

    International Nuclear Information System (INIS)

    Sharma, R.C.; Kumar, Pardeep

    1994-01-01

    Rayleigh-Taylor instability of electrically conducting Oldroydian viscoelastic fluid in porous medium is considered in the presence of a variable horizontal magnetic field. The cases of two uniform fluids separated by a horizontal boundary and exponentially varying density, viscosity and magnetic field are considered. In each case, the magnetic field succeeds in stabilizing certain wavenumber range which were unstable in the absence of magnetic field whereas the system is found to be stable for potentially stable configuration/stable stratifications. It is found that the stability criterion is independent of the effects of medium permeability, viscosity and viscoelasticity and is dependent on the orientation and magnitude of the magnetic field. The growth rates both increase for certain wavenumbers and decrease for different wavenumbers with the increase in kinematic viscosity, medium permeability, stress relaxation time and strain retardation time. (author). 5 refs

  19. NUMERICAL SIMULATIONS OF THE MAGNETIC RAYLEIGH-TAYLOR INSTABILITY IN THE KIPPENHAHN-SCHLÜTER PROMINENCE MODEL. I. FORMATION OF UPFLOWS

    International Nuclear Information System (INIS)

    Hillier, Andrew; Isobe, Hiroaki; Shibata, Kazunari; Berger, Thomas

    2012-01-01

    The launch of the Hinode satellite led to the discovery of rising plumes, dark in chromospheric lines, that propagate from large (∼10 Mm) bubbles that form at the base of quiescent prominences. The plumes move through a height of approximately 10 Mm while developing highly turbulent profiles. The magnetic Rayleigh-Taylor instability was hypothesized to be the mechanism that drives these flows. In this study, using three-dimensional (3D) MHD simulations, we investigate the nonlinear stability of the Kippenhahn-Schlüter prominence model for the interchange mode of the magnetic Rayleigh-Taylor instability. The model simulates the rise of a buoyant tube inside the quiescent prominence model, where the interchange of magnetic field lines becomes possible at the boundary between the buoyant tube and the prominence. Hillier et al. presented the initial results of this study, where upflows of constant velocity (maximum found 6 km s –1 ) and a maximum plume width ≈1.5 Mm which propagate through a height of approximately 6 Mm were found. Nonlinear interaction between plumes was found to be important for determining the plume dynamics. In this paper, using the results of ideal MHD simulations, we determine how the initial parameters for the model and buoyant tube affect the evolution of instability. We find that the 3D mode of the magnetic Rayleigh-Taylor instability grows, creating upflows aligned with the magnetic field of constant velocity (maximum found 7.3 km s –1 ). The width of the upflows is dependent on the initial conditions, with a range of 0.5-4 Mm which propagate through heights of 3-6 Mm. These results are in general agreement with the observations of the rising plumes.

  20. Growth of Rayleigh-Taylor and bulk convective instabilities in dynamics of plasma liners and pinches

    International Nuclear Information System (INIS)

    Bud'ko, A.B.; Velikovich, A.L.; Liberman, M.A.; Felber, F.S.

    1989-01-01

    Perturbation growth is studied for the initial, linear stage of an instability development in the course of a cylindrically-symmetric compression and expansion of plasma liners and Z-pinches with a sharp boundary. The hydrodynamic instabilities are Rayleigh-Taylor and bulk convective ones, the former being the most dengerous. Classification of the instability modes developing in accelerated plasmas, inclusing the local and global Rayleigh-Taylor modes, is given. The spectra of the instability growth rates are calculated for plasma liners and Z-pinches. The properties of the spectra appear to explain the filamentation and stratification of plasmas observed in the experiments with liners and Z-pinches. An axial magnetic field is shown to create a window of stability in the space of the flow parameters, where th Rayleigh-Taylor modes are fully suppressed by the magnetic shear, and the bulk convective ones - to a considerable extent. The axial magnetic field required to stabilize the implosion of a liner is estimated as B z0 =(10-30 kG)I(MA)/R 0 (cm), where I is the average current, R 0 - the initial radius of the liner

  1. Development of Rayleigh-Taylor and bulk convection instabilities in the dynamics of plasma liners and pinches

    International Nuclear Information System (INIS)

    Bud'ko, A.B.; Velikovich, A.L.; Liberman, M.A.; Felber, F.S.

    1989-01-01

    A solution is derived for the problem of the initial, linear stage of the growth of small perturbations in the course of the cylindrically symmetric compression and expansion of a plasma liner and a Z-pinch with a sharp boundary. In these systems, Rayleigh-Taylor instabilities localized near the plasma boundaries are the most dangerous. Bulk convective instabilities develop in addition to these Rayleigh-Taylor instabilities. The various instability modes, including local and global Rayleigh-Taylor modes, which grown in an accelerated plasma with distributed profiles of hydrodynamic variables, are classified. The spectra of the instability growth rates are calculated for plasma liners and Z-pinches. The shape of these spectra reveals an explanation of the stratification and filamentation of the plasma observed experimentally in pinches and liners. The imposition of a longitudinal magnetic field gives rise to a stability window in the space of the flow parameters. In this window, the Rayleigh-Taylor modes are suppressed completely by magnetic shear, while the bulk convective modes are suppressed to a significant extent

  2. Investigation of magnetic field effects on the mitigation of the magnetohydrodynamic Rayleigh-Taylor instability in fast z-pinch implosions

    International Nuclear Information System (INIS)

    Douglas, M.; Deeney, C.; Roderick, N.

    1999-01-01

    Numerical simulations have been carried out to investigate the role that magnetic field diffusion and ohmic heating have on the magnetohydrodynamic Rayleigh-Taylor (RT) development in fast z-pinch implosions. Previous work has indicated these terms can strongly influence the evolution of RT growth, leading to a reduction in RT amplitude, and an improvement in pinch performance. Indeed, Roderick et al have suggested that magnetic smoothing is an important mechanism in linear RT growth. To examine this in more detail, simulations are presented for a 1.4 mg, 25.0 mm diameter tungsten wire array imploded in the Saturn long pulse mode. The 130 ns implosion time of this calculation should enhance any mitigating effects that may be attributed to nonideal MHD. Calculations were performed using the 2D MHD code Mach2. The wire array was approximated by a right cylindrical slab of 1.0 mm width. Both a random density perturbation and single mode density perturbations were incorporated to initiate the instability. In the former case, a 5% cell-to-cell random perturbation was used. This allowed a range of modes to be initially present. In the single mode case, a 1.25 mm wavelength, on the order of the shell thickness, was defined. To isolate the contributions due to field diffusion, joule heating, and equation of state, simulations were run with and without ohmic heating using both constant and material-dependent spitzer resistivities. This analysis was then extended to look at the effect of such parameters on the nested shell load configuration. Detailed analysis of the simulations will be presented

  3. RADIATIVE RAYLEIGH-TAYLOR INSTABILITIES

    International Nuclear Information System (INIS)

    Jacquet, Emmanuel; Krumholz, Mark R.

    2011-01-01

    We perform analytic linear stability analyses of an interface separating two stratified media threaded by a radiation flux, a configuration relevant in several astrophysical contexts. We develop a general framework for analyzing such systems and obtain exact stability conditions in several limiting cases. In the optically thin, isothermal regime, where the discontinuity is chemical in nature (e.g., at the boundary of a radiation pressure-driven H II region), radiation acts as part of an effective gravitational field, and instability arises if the effective gravity per unit volume toward the interface overcomes that away from it. In the optically thick a diabaticregime where the total (gas plus radiation) specific entropy of a Lagrangian fluid element is conserved, for example at the edge of radiation pressure-driven bubble around a young massive star, we show that radiation acts like a modified equation of state and derive a generalized version of the classical Rayleigh-Taylor stability condition.

  4. Nonideal Rayleigh-Taylor mixing

    Energy Technology Data Exchange (ETDEWEB)

    Sharp, David Howland [Los Alamos National Laboratory; Lin, Hyun K [STONY BROOK UNIV.; Iwerks, Justin G [Los Alamos National Laboratory; Gliman, James G [Los Alamos National Laboratory; [NON LANL

    2009-01-01

    Rayleigh-Taylor mixing is a classical hydrodynamic Instability, which occurs when a light fluid pushes against a heavy fluid. The two main sources of nonideal behavior in Rayleigh-Taylor (RT) mixing are regularizations (physical and numerical) which produce deviations from a pure Euler equation, scale Invariant formulation, and non Ideal (i.e. experimental) initial conditions. The Kolmogorov theory of turbulence predicts stirring at all length scales for the Euler fluid equations without regularization. We Interpret mathematical theories of existence and non-uniqueness in this context, and we provide numerical evidence for dependence of the RT mixing rate on nonideal regularizations, in other words indeterminacy when modeled by Euler equations. Operationally, indeterminacy shows up as non unique solutions for RT mixing, parametrized by Schmidt and Prandtl numbers, In the large Reynolds number (Euler equation) limit. Verification and validation evidence is presented for the large eddy simulation algorithm used here. Mesh convergence depends on breaking the nonuniqueness with explicit use of the laminar Schmidt and PrandtJ numbers and their turbulent counterparts, defined in terms of subgrid scale models. The dependence of the mixing rate on the Schmidt and Prandtl numbers and other physical parameters will be illustrated. We demonstrate numerically the influence of initial conditions on the mixing rate. Both the dominant short wavelength Initial conditions and long wavelength perturbations are observed to playa role. By examination of two classes of experiments, we observe the absence of a single universal explanation, with long and short wavelength initial conditions, and the various physical and numerical regularizations contributing In different proportions In these two different contexts.

  5. Quantum effects on the Rayleigh-Taylor instability in a horizontal inhomogeneous rotating plasma

    International Nuclear Information System (INIS)

    Hoshoudy, G. A.

    2009-01-01

    The Rayleigh-Taylor instability is studied analytically in inhomogeneous plasma rotating uniformly in an external transverse magnetic field. The influence of the quantum mechanism is considered. For a stratified layer the linear growth rate is obtained. Some special cases that isolate the effect of various parameters on the growth rate of the Rayleigh-Taylor instability are discussed. It is shown that for some cases, the presence of the external transverse magnetic field beside the quantum effect will bring about more stability on the Rayleigh-Taylor instability.

  6. Overview of Rayleigh-Taylor instability

    Energy Technology Data Exchange (ETDEWEB)

    Sharp, D.H.

    1983-01-01

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

  7. Rayleigh-Taylor mixing in supernova experiments

    International Nuclear Information System (INIS)

    Swisher, N. C.; Abarzhi, S. I.; Kuranz, C. C.; Arnett, D.; Hurricane, O.; Remington, B. A.; Robey, H. F.

    2015-01-01

    We report a scrupulous analysis of data in supernova experiments that are conducted at high power laser facilities in order to study core-collapse supernova SN1987A. Parameters of the experimental system are properly scaled to investigate the interaction of a blast-wave with helium-hydrogen interface, and the induced Rayleigh-Taylor instability and Rayleigh-Taylor mixing of the denser and lighter fluids with time-dependent acceleration. We analyze all available experimental images of the Rayleigh-Taylor flow in supernova experiments and measure delicate features of the interfacial dynamics. A new scaling is identified for calibration of experimental data to enable their accurate analysis and comparisons. By properly accounting for the imprint of the experimental conditions, the data set size and statistics are substantially increased. New theoretical solutions are reported to describe asymptotic dynamics of Rayleigh-Taylor flow with time-dependent acceleration by applying theoretical analysis that considers symmetries and momentum transport. Good qualitative and quantitative agreement is achieved of the experimental data with the theory and simulations. Our study indicates that in supernova experiments Rayleigh-Taylor flow is in the mixing regime, the interface amplitude contributes substantially to the characteristic length scale for energy dissipation; Rayleigh-Taylor mixing keeps order

  8. Hydromagnetic Rayleigh-Taylor instability in cylindrical implosions

    International Nuclear Information System (INIS)

    Hwang, C.S.; Roderick, N.F.; Wu, M.W.

    1986-01-01

    Rayleigh-Taylor Instability in the (r,Θ) plane has been solved by the variational approach. Results are compared to the analytical solutions of two-region and three-region problems at the infinite radius. They show the magnetic stabilization effect. Growth rates in this plane are decreased by the effects of plasma shell thickness, plasma shell radius, magnetic tension, magnetic diffusion and finite density gradient of the plasma magnetic field interface. The most unstable mode number decreases when the radius of the plasma shell decreases

  9. Theoretical and Experimental Studies of Magneto-Rayleigh-Taylor Instabilities

    Energy Technology Data Exchange (ETDEWEB)

    Lau, Yue Ying [University of Michigan, Ann Arbor, MI (United States); Gilgenbach, Ronald [University of Michigan, Ann Arbor, MI (United States)

    2013-07-07

    Magneto-Rayleigh-Taylor instability (MRT) is important to magnetized target fusion, wire-array z-pinches, and equation-of-state studies using flyer plates or isentropic compression. It is also important to the study of the crab nebula. The investigators performed MRT experiments on thin foils, driven by the mega-ampere linear transformer driver (LTD) facility completed in their laboratory. This is the first 1-MA LTD in the USA. Initial experiments on the seeding of MRT were performed. Also completed was an analytic study of MRT for a finite plasma slab with arbitrary magnetic fields tangential to the interfaces. The effects of magnetic shear and feedthrough were analyzed.

  10. The role of Rayleigh-Taylor instabilities in filament threads

    Science.gov (United States)

    Terradas, J.; Oliver, R.; Ballester, J. L.

    2012-05-01

    Context. Many solar filaments and prominences show short-lived horizontal threads lying parallel to the photosphere. Aims: In this work the possible link between Rayleigh-Taylor instabilities and thread lifetimes is investigated. Methods: This is done by calculating the eigenmodes of a thread modelled as a Cartesian slab under the presence of gravity. An analytical dispersion relation is derived using the incompressible assumption for the magnetohydrodynamic (MHD) perturbations. Results: The system allows a mode that is always stable, independently of the value of the Alfvén speed in the thread. The character of this mode varies from being localised at the upper interface of the slab when the magnetic field is weak, to having a global nature and resembling the transverse kink mode when the magnetic field is strong. On the contrary, the slab model permits another mode that is unstable and localised at the lower interface when the magnetic field is weak. The growth rates of this mode can be very short, of the order of minutes for typical thread conditions. This Rayleigh-Taylor unstable mode becomes stable when the magnetic field is increased, and in the limit of strong magnetic field it is essentially a sausage magnetic mode. Conclusions: The gravity force might have a strong effect on the modes of oscillation of threads, depending on the value of the Alfvén speed. In the case of threads in quiescent filaments, where the Alfvén speed is presumably low, very short lifetimes are expected according to the slab model. In active region prominences, the stabilising effect of the magnetic tension might be enough to suppress the Rayleigh-Taylor instability for a wide range of wavelengths.

  11. Centrifugally Driven Rayleigh-Taylor Instability

    Science.gov (United States)

    Scase, Matthew; Hill, Richard

    2017-11-01

    The instability that develops at the interface between two fluids of differing density due to the rapid rotation of the system may be considered as a limit of high-rotation rate Rayleigh-Taylor instability. Previously the authors have considered the effect of rotation on a gravitationally dominated Rayleigh-Taylor instability and have shown that some growth modes of instability may be suppressed completely by the stabilizing effect of rotation (Phys. Rev. Fluids 2:024801, Sci. Rep. 5:11706). Here we consider the case of very high rotation rates and a negligible gravitational field. The initial condition is of a dense inner cylinder of fluid surrounded by a lighter layer of fluid. As the system is rotated about the generating axis of the cylinder, the dense inner fluid moves away from the axis and the familiar bubbles and spikes of Rayleigh-Taylor instability develop at the interface. The system may be thought of as a ``fluid-fluid centrifuge''. By developing a model based on an Orr-Sommerfeld equation, we consider the effects of viscosity, surface tension and interface diffusion on the growth rate and modes of instability. We show that under particular circumstances some modes may be stabilized. School of Mathematical Sciences.

  12. Nonlinear saturation of the Rayleigh Taylor instability

    International Nuclear Information System (INIS)

    Das, A.; Mahajan, S.; Kaw, P.; Sen, A.; Benkadda, S.; Verga, A.

    1997-01-01

    The problem of the nonlinear saturation of the 2 dimensional Rayleigh Taylor instability is re-examined to put various earlier results in a proper perspective. The existence of a variety of final states can be attributed to the differences in the choice of boundary conditions and initial conditions in earlier numerical modeling studies. Our own numerical simulations indicate that the RT instability saturates by the self consistent generation of shear flow even in situations (with periodic boundaries) where, in principle, an infinite amount of gravitational energy can be tapped. Such final states can be achieved for suitable values of the Prandtl number. (author)

  13. Anisotropy and Feedthrough in Magneto-Rayleigh-Taylor Instabilities

    Science.gov (United States)

    Weis, Matthew; Rittersdorf, Ian; Lau, Yue Ying; Zhang, Peng; Gilgenbach, Ronald; Zier, Jacob

    2011-10-01

    The magneto-Rayleigh-Taylor instability (MRT) in a finite slab is studied analytically using the ideal MHD model. The slab may be accelerated by an arbitrary combination of magnetic pressure and fluid pressure, thus allowing an arbitrary degree of anisotropy intrinsic to the acceleration mechanism. The magnetic field in different regions may assume arbitrary magnitude and direction tangential to the interface. In general, MRT retains robust growth if it exists. However, feedthrough may be substantially reduced if there are magnetic fields on both sides of the slab, and if the MRT mode invokes bending of the magnetic field lines. The analytically tractable eigenmode solutions allow an evaluation of the temporal evolution of MRT from random initial surface roughness. Work supported by DoE award DE-SC0002590, NSF award PHY 0903340, and by DoE through Sandia National Lab awards 240985 and 76822 to U. of Michigan. JCZ was supported by an NPSC fellowship through Sandia.

  14. Mode coupling in nonlinear Rayleigh--Taylor instability

    International Nuclear Information System (INIS)

    Ofer, D.; Shvarts, D.; Zinamon, Z.; Orszag, S.A.

    1992-01-01

    This paper studies the interaction of a small number of modes in the two-fluid Rayleigh--Taylor instability at relatively late stages of development, i.e., the nonlinear regime, using a two-dimensional hydrodynamic code incorporating a front-tracking scheme. It is found that the interaction of modes can greatly affect the amount of mixing and may even reduce the width of the mixing region. This interaction is both relatively long range in wave-number space and also acts in both directions, i.e., short wavelengths affect long wavelengths and vice versa. Three distinct stages of interaction have been identified, including substantial interaction among modes some of which may still be in their classical (single mode) ''linear'' phase

  15. Effects of shock waves on Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Zhang Yongtao; Shu Chiwang; Zhou Ye

    2006-01-01

    A numerical simulation of two-dimensional compressible Navier-Stokes equations using a high-order weighted essentially nonoscillatory finite difference shock capturing scheme is carried out in this paper, to study the effect of shock waves on the development of Rayleigh-Taylor instability. Shocks with different Mach numbers are introduced ahead or behind the Rayleigh-Taylor interface, and their effect on the transition to instability is demonstrated and compared. It is observed that shock waves can speed up the transition to instability for the Rayleigh-Taylor interface significantly. Stronger shocks are more effective in this speed-up process

  16. 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.

  17. Manipulating Rayleigh-Taylor Growth Using Adjoints

    Science.gov (United States)

    Kord, Ali; Capecelatro, Jesse

    2017-11-01

    It has been observed that initial interfacial perturbations affect the growth of Rayleigh-Taylor (RT) instabilities. However, it remains to be seen to what extent the perturbations alter the RT growth rate. Direct numerical simulations (DNS) provide a powerful means for studying the effects of initial conditions (IC) on the growth rate. However, a brute-force approach for identifying optimal initial perturbations is not practical via DNS. In addition, identifying sensitivity of the RT growth to the large number of parameters used in defining the IC is computationally expensive. A discrete adjoint is formulated to measure sensitivities of multi-mode RT growth to ICs in a high-order finite difference framework. The sensitivity is used as a search direction for adjusting the initial perturbations to both maximize and suppress the RT growth rate during its non-linear regime. The modes that contribute the greatest sensitivity are identified, and optimized perturbation energy spectrum are reported. PhD Student, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI.

  18. Magneto-Rayleigh-Taylor instability in solid media

    International Nuclear Information System (INIS)

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

    2014-01-01

    A linear analysis of the magneto-Rayleigh-Taylor instability at the interface between a Newtonian fluid and an elastic-plastic solid is performed by considering a uniform magnetic B → , parallel to the interface, which has diffused into the fluid but not into the solid. It is found that the magnetic field attributes elastic properties to the viscous fluid which enhance the stability region by stabilizing all the perturbation wavelengths shorter than λ 0 ∝B 2 for any initial perturbation amplitude. Longer wavelengths are stabilized by the mechanical properties of the solid provided that the initial perturbation wavelength is smaller than a threshold value determined by the yield strength and the shear modulus of the solid. Beyond this threshold, the amplitude grows initially with a growth rate reduced by the solid strength properties. However, such properties do not affect the asymptotic growth rate which is only determined by the magnetic field and the fluid viscosity. The described physical situation intends to resemble some of the features present in recent experiments involving the magnetic shockless acceleration of flyers plates

  19. Simulation of Rayleigh-Taylor instability growth rate of laser accelerated plant target. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Bel`kov, S.A.; Bondarenko, S.V.; Vinokurov, O.A.; Kochemasov, G.G.; Mkhitarian, L.S.

    1996-09-01

    This report presents the research results for the time point when the Rayleigh-Taylor instability converts to the nonlinear stage as well as the computational results for the interaction of two modes of Rayleigh-Taylor instability when initial perturbations are concentrated at the ablation front (problem (a)) and on the rear side (problem (b)) of the plane target. As was shown in the report for the first phase, for a target of 3 {mu}m thick the existence time of the nonlinear stage is extremely low and does not allow to track the evolution pattern. In it was shown that the plane target with {Delta}{sub 0}=5 {mu}m is more preferable for this goal. Therefore all the computations presented here relate to the target with the indicated thickness. The laser pulse parameters are remained unchanged J{sub L}=10{sup 15} W/cm{sup 2}, {lambda}=0.35 {mu}m.

  20. Role of parallel flow curvature on the mitigation of Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Sarmah, D.; Sen, S.; Cairns, R.A.

    2001-01-01

    The effect of a radially varying parallel equilibrium flow on the stability of the Rayleigh-Taylor (RT) mode is studied analytically in the presence of a sheared magnetic field. It is shown that the parallel flow curvature can completely stabilize the RT mode. The flow curvature also has a robust effect on the radial structure of the mode. Possible implications of these theoretical findings to recent experiments are also discussed

  1. Potential Flow Model for Compressible Stratified Rayleigh-Taylor Instability

    Science.gov (United States)

    Rydquist, Grant; Reckinger, Scott; Owkes, Mark; Wieland, Scott

    2017-11-01

    The Rayleigh-Taylor Instability (RTI) is an instability that occurs when a heavy fluid lies on top of a lighter fluid in a gravitational field, or a gravity-like acceleration. It occurs in many fluid flows of a highly compressive nature. In this study potential flow analysis (PFA) is used to model the early stages of RTI growth for compressible fluids. In the localized region near the bubble tip, the effects of vorticity are negligible, so PFA is applicable, as opposed to later stages where the induced velocity due to vortices generated from the growth of the instability dominate the flow. The incompressible PFA is extended for compressibility effects by applying the growth rate and the associated perturbation spatial decay from compressible linear stability theory. The PFA model predicts theoretical values for a bubble terminal velocity for single-mode compressible RTI, dependent upon the Atwood (A) and Mach (M) numbers, which is a parameter that measures both the strength of the stratification and intrinsic compressibility. The theoretical bubble terminal velocities are compared against numerical simulations. The PFA model correctly predicts the M dependence at high A, but the model must be further extended to include additional physics to capture the behavior at low A. Undergraduate Scholars Program - Montana State University.

  2. The Rayleigh-Taylor instability in the spherical pinch

    International Nuclear Information System (INIS)

    Chen, H.B.; Hilko, B.; Panarella, E.

    1994-01-01

    The spherical pinch (SP) concept is an outgrowth of the inertial confinement model (ICF). Unlike the ICF where instabilities, especially the Rayleigh-Taylor instability, have been studied extensively, the instability study of the spherical pinch has just begun. The Raleigh-Taylor instability is investigated for the first time in the SP in the present work. By using the simple condition for the Rayleigh-Taylor instability ∇p · ∇p < O (density and pressure gradients have opposite direction), we have qualitatively identified the regions for development of instabilities in the SP. It is found that the explosion phase (central discharge) is stable and instabilities take place in the imploding phase. However, the growth rate for the instability is not in exponential form, and the appearance of the Rayleigh-Taylor instability does not prevent the main shock wave from converging to the center of the sphere

  3. Numerical simulation of Rayleigh-Taylor turbulent mixing layers

    International Nuclear Information System (INIS)

    Poujade, O.; Lardjane, N.; Peybernes, M.; Boulet, M.

    2009-01-01

    Accelerations in actual Rayleigh-Taylor instabilities are often variable. This article focuses on a particular class of variable accelerations where g(t) ∝ t n . A reference database is built from high resolution hydrodynamic numerical simulations. The successful comparison with a simple OD analytical model and the statistical 2SFK (2-Structure, 2-Fluid, 2-Turbulence) turbulence model is provided. Moreover, we show the difference between the mechanism at play in the Rayleigh-Taylor turbulent mixing zone and Kolmogorov's in the self similar developed turbulent regime. (authors)

  4. Rayleigh-Taylor convective overturn in stellar collapse

    International Nuclear Information System (INIS)

    Bruenn, S.W.; Buchler, J.R.; Livio, M.

    1979-01-01

    Rayleigh--Taylor convective overturn in collapsing stellar cores is modeled with a one-dimensional parametrization. The results of a numerical hydrodynamic study are very encouraging and indicate that such an overturn could well be a dominant feature in the supernova explosion mechanism

  5. RAYLEIGH-TAYLOR INSTABILITY IN PARTIALLY IONIZED COMPRESSIBLE PLASMAS

    Energy Technology Data Exchange (ETDEWEB)

    Diaz, A. J. [Instituto de Astrofisica de Canarias, 38205, C/ Via Lactea, s/n, La Laguna, Tenerife (Spain); Soler, R. [Centre for Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, 3001 Leuven (Belgium); Ballester, J. L., E-mail: tdiaz@iac.es, E-mail: roberto.soler@wis.kuleuven.be, E-mail: dfsjlb0@uib.es [Departament de Fisica, Universitat de les Illes Balears, E-07122 Palma de Mallorca (Spain)

    2012-07-20

    We study the modification of the classical criterion for the linear onset and growing rate of the Rayleigh-Taylor instability (RTI) in a partially ionized plasma in the two-fluid description. The plasma is composed of a neutral fluid and an electron-ion fluid, coupled by means of particle collisions. The governing linear equations and appropriate boundary conditions, including gravitational terms, are derived and applied to the case of the RTI in a single interface between two partially ionized plasmas. The limits of collisionless, no gravity, and incompressible fluids are checked before addressing the general case. We find that both compressibility and ion-neutral collisions lower the linear growth rate, but do not affect the critical threshold of the onset of the RTI. The configuration is always unstable when a lighter plasma is below a heavier plasma regardless the value of the magnetic field strength, the ionization degree, and the ion-neutral collision frequency. However, ion-neutral collisions have a strong impact on the RTI growth rate, which can be decreased by an order of magnitude compared to the value in the collisionless case. Ion-neutral collisions are necessary to accurately describe the evolution of the RTI in partially ionized plasmas such as prominences. The timescale for the development of the instability is much longer than in the classical incompressible fully ionized case. This result may explain the existence of prominence fine structures with life times of the order of 30 minutes. The timescales derived from the classical theory are about one order of magnitude shorter and incompatible with the observed life times.

  6. Rayleigh-Taylor/gravitational instability in dense magnetoplasmas

    International Nuclear Information System (INIS)

    Ali, S.; Ahmed, Z.; Mirza, Arshad M.; Ahmad, I.

    2009-01-01

    The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

  7. Rayleigh-Taylor instability of cylindrical jets with radial motion

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Xiang M. [GE Nuclear, Wilmington, NC (United States); Schrock, V.E.; Peterson, P.F. [Univ. of California, Berkeley, CA (United States)

    1995-09-01

    Rayleigh-Taylor instability of an interface between fluids with different densities subjected to accelleration normal to itself has interested researchers for almost a century. The classic analyses of a flat interface by Rayleigh and Taylor have shown that this type of instability depends on the direction of acceleration and the density differences of the two fluids. Plesset later analyzed the stability of a spherically symmetric flows (and a spherical interface) and concluded that the instability also depends on the velocity of the interface as well as the direction and magnitude of radial acceleration. The instability induced by radial motion in cylindrical systems seems to have been neglected by previous researchers. This paper analyzes the Rayleigh-Taylor type of the spherical case, the radial velocity also plays an important role. As an application, the example of a liquid jet surface in an Inertial Confinement Fusion (ICF) reactor design is analyzed.

  8. Rayleigh-Taylor/gravitational instability in dense magnetoplasmas

    Energy Technology Data Exchange (ETDEWEB)

    Ali, S., E-mail: shahid.ali@ncp.edu.p [National Centre for Physics, Quaid-i-Azam University Campus, Islamabad (Pakistan); IPFN, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Ahmed, Z. [COMSATS Institute of Information Technology, Department of Physics, Wah Campus (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Physics Department, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Ahmad, I. [COMSATS Institute of Information Technology, Department of Physics, Islamabad Campus (Pakistan)

    2009-08-10

    The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

  9. Stochastic model of Rayleigh-Taylor turbulent mixing

    International Nuclear Information System (INIS)

    Abarzhi, S.I.; Cadjan, M.; Fedotov, S.

    2007-01-01

    We propose a stochastic model to describe the random character of the dissipation process in Rayleigh-Taylor turbulent mixing. The parameter alpha, used conventionally to characterize the mixing growth-rate, is not a universal constant and is very sensitive to the statistical properties of the dissipation. The ratio between the rates of momentum loss and momentum gain is the statistic invariant and a robust parameter to diagnose with or without turbulent diffusion accounted for

  10. Rayleigh-Taylor instability in a visco-plastic fluid

    International Nuclear Information System (INIS)

    Demianov, A Yu; Doludenko, A N; Son, E E; Inogamov, N A

    2010-01-01

    The Rayleigh-Taylor and Richtmyer-Meshkov instabilities of a visco-plastic fluid are discussed. The Bingham model is used as an effective rheological model which takes into account plastic effects. For the purposes of numerical simulation a one-mode disturbance of the contact surface between two fluids is considered. The main goal of this work is to construct numerical 2D and 3D models and to obtain the relationship between yield stress and the development of instability.

  11. Rayleigh-Taylor instability in a visco-plastic fluid

    Science.gov (United States)

    Demianov, A. Yu; Doludenko, A. N.; Inogamov, N. A.; Son, E. E.

    2010-12-01

    The Rayleigh-Taylor and Richtmyer-Meshkov instabilities of a visco-plastic fluid are discussed. The Bingham model is used as an effective rheological model which takes into account plastic effects. For the purposes of numerical simulation a one-mode disturbance of the contact surface between two fluids is considered. The main goal of this work is to construct numerical 2D and 3D models and to obtain the relationship between yield stress and the development of instability.

  12. Preliminary study of Rayleigh-Taylor instability in wire-array Z-pinch

    International Nuclear Information System (INIS)

    He Kaihui; Feng Kaiming; Li Qiang; Gao Chunming

    2000-01-01

    It is important to research into the MHD Rayleigh-Taylor instability developed in Z-pinch implosion. A snowplough model of the single wire Z-pinch is presented. The perturbation amplitude of Rayleigh-Taylor instability in the wire-array Z-pinch is analyzed quantitatively. Sheared axial flow is put forward to mitigate and reduce the Rayleigh-Taylor instability. And other approaches used to mitigate MHD instability in such a super-fast process are explored

  13. Shear flow stabilization of the hydromagnetic Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Roderick, N.F.; Shumlak, U.; Douglas, M.; Peterkin, R.E. Jr.; Ruden, E.

    1997-01-01

    Numerical simulations have indicated that shear flow may help stabilize the hydromagnetic Rayleigh-Taylor instability in imploding plasma z-pinches. A simple extension to a model presented in Chandrasekhar has been developed to study the linear stability of incompressible plasma subjected to both a shear flow and acceleration. The model has been used to investigate the stability plasma implosion schemes using externally imposed velocity shear which develops from the plasma flow itself. Specific parameters were chosen to represent plasma implosions driven by the Saturn and PBFA-Z, pulsed power generators at Sandia National Laboratories. Results indicate a high shear is necessary to stabilize the z-pinch implosions studied

  14. Statistical approach of weakly nonlinear ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Garnier, J.; Masse, L.

    2005-01-01

    A weakly nonlinear model is proposed for the Rayleigh-Taylor instability in presence of ablation and thermal transport. The nonlinear effects for a single-mode disturbance are computed, included the nonlinear correction to the exponential growth of the fundamental modulation. Mode coupling in the spectrum of a multimode disturbance is thoroughly analyzed by a statistical approach. The exponential growth of the linear regime is shown to be reduced by the nonlinear mode coupling. The saturation amplitude is around 0.1λ for long wavelengths, but higher for short instable wavelengths in the ablative regime

  15. Rayleigh-Taylor instability in accelerated elastic-solid slabs

    Science.gov (United States)

    Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

    2017-12-01

    We develop the linear theory for the asymptotic growth of the incompressible Rayleigh-Taylor instability of an accelerated solid slab of density ρ2, shear modulus G , and thickness h , placed over a semi-infinite ideal fluid of density ρ110.1007/s000330050121] to arbitrary values of AT and unveil the singular feature of an instability threshold below which the slab is stable for any perturbation wavelength. As a consequence, an accelerated elastic-solid slab is stable if ρ2g h /G ≤2 (1 -AT) /AT .

  16. Three-dimensional Rayleigh-Taylor convection of miscible fluids in a porous medium

    Science.gov (United States)

    Suekane, Tetsuya; Nakanishi, Yuji; Wang, Lei

    2017-11-01

    Natural convection of miscible fluids in a porous medium is relevant for fields, such as geoscience and geoengineering, and for the geological storage of CO2. In this study, we use X-ray computer tomography to visualize 3D fingering structures associated with the Rayleigh-Taylor instability between miscible fluids in a porous medium. In the early stages of the onset of the Rayleigh-Taylor instability, a fine crinkling pattern gradually appears at the interface. As the wavelength and amplitude increase, descending fingers form on the interface and extend vertically downward; moreover, ascending and highly symmetric fingers form. The adjacent fingers are cylindrical in shape and coalesce to form large fingers. Fingers appearing on the interface tend to become finer with increasing Rayleigh number, which is consistent with linear perturbation theory. If the Péclet number exceeds 10, the transverse dispersion increases the finger diameter and enhances finger coalescence, strongly impacting the decay in finger number density. When mechanical dispersion is negligible, the finger-extension velocity, the mass-transfer rate, and the onset time scale with Rayleigh number. Mechanical dispersion not only reduces the onset time but also enhances mass transport, which indicates that mechanical dispersion influences the long-term dissolution process of CO2 injected into aquifers.

  17. Model for the saturation of the hydromagnetic Rayleigh--Taylor instability

    International Nuclear Information System (INIS)

    Roderick, N.F.; Hussey, T.W.

    1984-01-01

    The saturation of the hydromagnetic Rayleigh--Taylor instability is caused by the reduction of driving current in the bubble region between the spikes formed as the instability develops. For short wavelengths linear magnetic field diffusion provides the necessary smoothing of the magnetic field to reduce the driving force. For wavelengths longer than the magnetic field diffusion length, the current is shorted through material which expands into the bubble region. This initially low density accumulates in the bubble and eventually provides a source of sufficiently high conductivity plasma which reduces the magnetic field penetration to the front of the bubble. Simple analytic models have been developed to verify and and quantify these predictions. These models have been compared with two-dimensional magnetohydrodynamic calculations for imploding plasma shells and give good agreement with these more detailed simulations

  18. Nonlinear interaction of Rayleigh--Taylor and shear instabilities

    International Nuclear Information System (INIS)

    Finn, J.M.

    1993-01-01

    Results on the nonlinear behavior of the Rayleigh--Taylor instability and consequent development of shear flow by the shear instability [Phys. Fluids B 4, 488 (1992)] are presented. It is found that the shear flow is generated at sufficient amplitude to reduce greatly the convective transport. For high viscosity, the time-asymptotic state consists of an equilibrium with shear flow and vortex flow (with islands, or ''cat's eyes''), or a relaxation oscillation involving an interplay between the shear instability and the Rayleigh--Taylor instability in the presence of shear. For low viscosity, the dominant feature is a high-frequency nonlinear standing wave consisting of convective vortices localized near the top and bottom boundaries. The localization of these vortices is due to the smaller shear near the boundary regions. The convective transport is largest around these convective vortices near the boundary and there is a region of good confinement near the center. The possible relevance of this behavior to the H mode and edge-localized modes (ELM's) in the tokamak edge region is discussed

  19. 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)

  20. Rayleigh-Taylor convection in confined porous media

    Science.gov (United States)

    Zonta, Francesco; de Paoli, Marco; Soldati, Alfredo

    2017-11-01

    Motivated by the dissolution phenomena occurring during carbon sequestration processes, we analyze Rayleigh-Taylor convection in isotropic porous media. In the Rayleigh-Taylor configuration, a layer of dense fluid (CO2+brine) lyes on top of a layer of light fluid (brine). The velocity field is computed with the Darcy law, whereas the concentration field is determined by the advection-diffusion equation. We used a pseudospectral scheme (Fourier discretization in periodic direction and Chebyshev polynomial in wall-normal direction) to run Direct Numerical Simulations (DNS) of the present system. We focused in particular on the behavior of the mixing length h (the tip-to-rear finger distance), a fundamental quantity to characterize all the transfer phenomena (solute, convection and energy) occurring in the analyzed case. In particular, we observed that the time behavior of h is twofold: during the initial transient evolution, h has a self similar universal behavior; later, due to the presence of boundaries, the behavior becomes more complex and hard to predict. Physical implications of the present results on dissolution modeling approaches will be also addressed.

  1. 2D HYDRA Calculations of Magneto-Rayleigh-Taylor Growth and Feedthrough in Cylindrical Liners

    Science.gov (United States)

    Weis, Matthew; Zhang, Peng; Lau, Y. Y.; Gilgenbach, Ronald; Peterson, Kyle; Hess, Mark

    2014-10-01

    Cylindrical liner implosions are susceptible to the magneto-Rayleigh-Taylor instability (MRT), along with the azimuthal current-carrying modes (sausage, kink, etc). ``Feedthrough'' of these instabilities has a strong influence on the integrity of the liner/fuel interface in the magnetized liner inertial fusion concept (MagLIF). The linearized ideal MHD equations can be solved to quantify these effects, including the presence of an effective gravity and an axial magnetic field. We investigate the potential of this field to mitigate feedthrough, due to MRT growth from various initial surface finishes (seeded, rough), throughout the implosion using our analytic results and the LLNL code, HYDRA. We will present both low and high convergence cases. Lastly, we illustrate the effect shock compression can have on feedthrough in seeded liners for various fill gases (cold and pre-heated) and magnetic field configurations. M. R. Weis was supported by the Sandia National Laboratories.

  2. Rayleigh-Taylor analysis in a laser-induced plasma

    International Nuclear Information System (INIS)

    Marin, R A; Gonzales, C A; Riascos, H

    2012-01-01

    We report the conditions (plasma parameters) under which the Rayleigh-Taylor Instability (RTI) develops in an Al plasma produced by a Nd:Yag pulsed laser with a fluence range of 1 to 4 J/cm 2 , wavelength of 1064nm and 10Hz repetition rate. The used data correspond to different pressure values of the ambient N atmosphere. From previous works, we took the RTI growth rate form. From the perturbation theory the instability amplitude is proportional to e -ηt . Using the drag model, we calculated the plume dynamics equations integrating the instability term and plotted the instability growth profile with the delay time values to get critical numbers for it, in order to show under which conditions the RTI appears.

  3. Simulation of Rayleigh--Taylor flows using vortex blobs

    International Nuclear Information System (INIS)

    Kerr, R.M.

    1988-01-01

    An inviscid boundary-integral method is modified in order to study the single-scale Rayleigh--Taylor instability for arbitrary Atwood number. The primary modification uses vortex blobs to smooth the Green's function and suppress a finite time singularity in the curvature. Additional modifications to earlier codes such as using second-order central differences along the interface to accommodate spikes in the vorticity and spreading the nodes evenly along the interface to suppress clustering of nodes are designed to maintain resolution and accuracy. To achieve second-order accuracy in time when the nodes are spread, an extra predictor step is needed that shifts the nodes before the variables are advanced. The method successfully follows the development of a single mode to states with asymptotic velocities for the bubble and spike that depend on the Atwood number and are independent of the blob size. Incipient droplet formation is observed. copyright 1988 Academic Press, Inc

  4. Nonlinear Rayleigh-Taylor growth in converging geometry

    International Nuclear Information System (INIS)

    Clark, Daniel S.; Tabak, Max

    2005-01-01

    The early nonlinear phase of Rayleigh-Taylor growth is typically described in terms of the classic Layzer model in which bubbles of light fluid rise into the heavy fluid at a constant rate determined by the bubble radius and the gravitational acceleration. However, this model is strictly valid only for planar interfaces and hence ignores any effects that might be introduced by the spherically converging interfaces of interest in inertial confinement fusion and various astrophysical phenomena. Here, a generalization of the Layzer nonlinear bubble rise rate is given for a self-similar spherically converging flow of the type studied by Kidder. A simple formula for the bubble amplitude is found showing that, while the bubble initially rises with a constant velocity similar to the Layzer result, during the late phase of the implosion, an acceleration of the bubble rise rate occurs. The bubble rise rate is verified by comparison with numerical hydrodynamics simulations

  5. Nonlinear Rayleigh-Taylor growth in convergine geometry

    International Nuclear Information System (INIS)

    Clark, D S; Tabak, M

    2005-05-01

    The early nonlinear phase of Rayleigh-Taylor growth is typically described in terms of the classic Layzer model in which bubbles of light fluid rise into the heavy fluid at a constant rate determined by the bubble radius and the gravitational acceleration. However, this model is strictly valid only for planar interfaces and hence ignores any effects which might be introduced by the spherically converging interfaces of interest in inertial confinement fusion. Here a generalization of the Layzer nonlinear bubble rise rate is given for a self-similar spherically converging flow of the type studied by Kidder. A simple formula for the bubble amplitude is found showing that, while the bubble initially rises with a constant velocity similar to the Layzer result, during the late phase of the implosion, an acceleration of the bubble rise rate occurs. The bubble rise rate is verified by comparison with numerical hydrodynamics simulations

  6. THE RAYLEIGH-TAYLOR INSTABILITY IN SMALL ASPECT RATIO CONTAINERS

    Energy Technology Data Exchange (ETDEWEB)

    RIVERA, MICHAEL K. [Los Alamos National Laboratory; ECKE, ROBERT E. [Los Alamos National Laboratory

    2007-01-22

    We present experimental measurements of density and velocity obtained from the mixing zone of buoyancy driven turbulence initiated by the Rayleigh-Taylor instability in a small aspect ration chamber (a chamber who's vertical height is significantly larger than its lateral dimesion). The mixing front propogates at a slightly slower rate than the expected t{sup 2} behavior obtained from earlier experiments and numerics. Once the front has propogated significantly far away, we observe that the mixing zone develops to a statistically stationary state. In this stationary state, the spectral distributions of energy and density deviate from the familiar k{sup -5/3} ubiquitous to turbulence in three dimensions.

  7. Unstable Titan-generated Rayleigh-Taylor Lakes Impact Ice

    Science.gov (United States)

    Umurhan, O. M.; Korycansky, D. G.; Zahnle, K. J.

    2014-12-01

    The evolution of surface morphology on Titan, Triton, and other worlds is strongly influenced by the interplay of various fluid dynamical processes. Specifically, overturning instabilities can easily arise due to the special circumstances of landform evolution that probably occurred on these worlds. On Titan, large impacts that formed basins like Menrva crater (and possibly Hotei Regio) would have generated impact-melt ice lakes unstably arranged over less dense ice. Cantaloupe terrains, for example as seen on Triton, may be the result of condensation of volatiles (methane, nitrogen) leading to unstably stratified layers of different compositions and densities. In each of these cases, Rayleigh-Taylor instabilities leading to large scale diapirism may be at play. In addition to the dynamics of these instabilities, other physical effects (e.g. heat diffusion, freezing/melting, porosity, temperature dependent viscosity) likely play an important role in the evolution of these features. In this ongoing study, we examine the properties of unstably stratified fluids in which the lower less-dense ice has a temperature dependent viscosity. Surprisingly, we find that there exists an optimal disturbance length scale corresponding to the fastest growth of the Rayleigh-Taylor instability. For unstably stratified layers of water (low viscosity heavy liquid lying above an ice whose viscosity increases with depth) the fastest growing mode corresponds to 40-60 km scales with overturn times of approximately 100 days. We present a detailed numerical stability analysis in a corresponding Boussinessq model (in the creeping flow limit) incorporating thermal conduction and latent heat release and we examine the stability properties surveying a variety of parameters. We have also developed a two-dimensional numerical code (a hybrid spectral/compact-differencing scheme) to model the evolution of such systems for which we shall present preliminary numerical results depicting the outcome of

  8. Experimental investigation of turbulent mixing by Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Youngs, D.L.

    1992-01-01

    A key feature of compressible turbulent mixing is the generation of vorticity via the ∇px ∇(1/ρ) term. This source of vorticity is also present in incompressible flows involving the mixing of fluids of different density, for example Rayleigh-Taylor unstable flows. This paper gives a summary of an experimental investigation of turbulent mixing at a plane boundary between two fluids, of densities ρ 1 , and ρ 2 . (ρ 1 > ρ 2 ) due to Rayleigh-Taylor instability. The two fluids are near incompressible and mixing occurs when an approximately constant acceleration, g, is applied normal to the interface with direction from fluid 2 to fluid 1. Full details of the experimental programme are given in a set of three reports. Some of the earlier experiments are also described by Read. Previous experimental work and much of the theoretical research has concentrated on studying the growth of the instability from a single wavelength perturbation rather than turbulent mixing. Notable exceptions are published in the Russian literature. A related process, turbulent mixing induced by the passage of shock waves though an interface between fluids of different density is described by Andronov et al. The major purpose of the experiments described here was to study the evolution of the instability from small random perturbations where it is found that large and larger structures appear as time proceeds. A novel technique was used to provide the desired acceleration. The two fluids were enclosed in a rectangular tank, the lighter fluid 2 initially resting on top of the denser fluid 1. One or more rocket motors were then used to drive the tank vertically downwards. The aim of the experimental programme is to provide data for the calibration of a turbulence model used to predict mixing in real situations

  9. Two-dimensional simulation of the hydromagnetic Rayleigh-Taylor instability in an imploding foil plasma

    International Nuclear Information System (INIS)

    Roderick, N.F.; Hussey, T.W.; Faehl, R.J.; Boyd, R.W.

    1978-01-01

    Two-dimensional (r-z) magnetohydrodynamic simulations of the electromagnetic implosion of metallic foil plasmas show, for certain initial configurations, a tendency to develop large-amplitude perturbations characteristic of the hydromagnetic Rayleigh-Taylor instability. These perturbations develop at the plasma magnetic field interface for plasma configurations where the density gradient scale length, the characteristic dimension for the instability, is short. The effects on the plasma dynamics of the implosion will be discussed for several initial foil configurations. In general, the growth rates and linear mode structure are found to be influenced by the plasma shell thickness and density gradient scale length, in agreement with theory. The most destructive modes are found to be those with wavelengths of the order of the plasma shell thickness

  10. Effect of FLR correction on Rayleigh -Taylor instability of quantum and stratified plasma

    International Nuclear Information System (INIS)

    Sharma, P.K.; Tiwari, Anita; Argal, Shraddha; Chhajlani, R.K.

    2013-01-01

    The Rayleigh Taylor instability of stratified incompressible fluids is studied in presence of FLR Correction and quantum effects in bounded medium. The Quantum magneto hydrodynamic equations of the problem are solved by using normal mode analysis method. A dispersion relation is carried out for the case where plasma is bounded by two rigid planes z = 0 and z = h. The dispersion relation is obtained in dimensionless form to discuss the growth rate of Rayleigh Taylor instability in presence of FLR Correction and quantum effects. The stabilizing or destabilizing behavior of quantum effect and FLR correction on the Rayleigh Taylor instability is analyzed. (author)

  11. Ablation front rayleigh taylor dispersion curve in indirect drive

    International Nuclear Information System (INIS)

    Budil, K.S.; Lasinski, B.; Edwards, M.J.; Wan, A.S.; Remington, B.A.; Weber, S.V.; Glendinning, S.G.; Suter, L.; Stry, P.

    2000-01-01

    The Rayleigh-Taylor (RT) instability, which occurs when a lower-density fluid accelerates a higher-density layer, is common in nature. At an ablation front a sharp reduction in the growth rate of the instability at short wave-lengths can occur, in marked contrast to the classical case where growth rates are highest at the shortest wavelengths. Theoretical and numerical investigations of the ablative RT instability are numerous and differ considerably on the level of stabilization expected. We present here the results of a series of laser experiments designed to probe the roll-over and cutoff region of the ablation-front RT dispersion curve in indirect drive. Aluminum foils with imposed sinusoidal perturbations ranging in wavelength from 10 to 70 pm were ablatively accelerated with a radiation drive generated in a gold cylindrical hohlraum. A strong shock wave compresses the package followed by an ∼2 ns period of roughly constant acceleration and the experiment is diagnosed via face-on radiography. Perturbations with wavelengths (ge) 20 (micro)m experienced substantial growth during the acceleration phase while shorter wavelengths showed a sharp drop off in overall growth. These experimental results compared favorably to calculations with a 2-D radiation-hydrodynamics code, however, the growth is significantly affected by the rippled shock launched by the drive. We performed numerical simulations to elucidate the influence of the rippled shock wave on the eventual growth of the perturbations, allowing comparisons to the analytic model developed by Betti et al. This combination of experiments, simulations and analytic modeling illustrates the qualitative simplicity yet quantitative complexity of the compressible RT instability. We have measured the Rayleigh-Taylor (RT) dispersion curve for a radiatively-driven sample in a series of experiments on the Nova laser facility. Planar aluminum foils were ablatively-accelerated and the subsequent perturbation growth was

  12. Direct numerical simulation of the Rayleigh-Taylor instability with the spectral element method

    International Nuclear Information System (INIS)

    Zhang Xu; Tan Duowang

    2009-01-01

    A novel method is proposed to simulate Rayleigh-Taylor instabilities using a specially-developed unsteady three-dimensional high-order spectral element method code. The numerical model used consists of Navier-Stokes equations and a transport-diffusive equation. The code is first validated with the results of linear stability perturbation theory. Then several characteristics of the Rayleigh-Taylor instabilities are studied using this three-dimensional unsteady code, including instantaneous turbulent structures and statistical turbulent mixing heights under different initial wave numbers. These results indicate that turbulent structures of Rayleigh-Taylor instabilities are strongly dependent on the initial conditions. The results also suggest that a high-order numerical method should provide the capability of simulating small scale fluctuations of Rayleigh-Taylor instabilities of turbulent flows. (authors)

  13. Direct Numerical Simulations of Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Livescu, D; Wei, T; Petersen, M R

    2011-01-01

    The development of the Rayleigh-Taylor mixing layer is studied using data from an extensive new set of Direct Numerical Simulations (DNS), performed on the 0.5 Petaflops, 150k compute cores BG/L Dawn supercomputer at Lawrence Livermore National Laboratory. This includes a suite of simulations with grid size of 1024 2 × 4608 and Atwood number ranging from 0.04 to 0.9, in order to examine small departures from the Boussinesq approximation as well as large Atwood number effects, and a high resolution simulation of grid size 4096 2 × 4032 and Atwood number of 0.75. After the layer width had developed substantially, additional branched simulations have been run under reversed and zero gravity conditions. While the bulk of the results will be published elsewhere, here we present preliminary results on: 1) the long-standing open question regarding the discrepancy between the numerically and experimentally measured mixing layer growth rates and 2) mixing characteristics.

  14. GRAVITATIONALLY UNSTABLE FLAMES: RAYLEIGH-TAYLOR STRETCHING VERSUS TURBULENT WRINKLING

    International Nuclear Information System (INIS)

    Hicks, E. P.; Rosner, R.

    2013-01-01

    In this paper, we provide support for the Rayleigh-Taylor-(RT)-based subgrid model used in full-star simulations of deflagrations in Type Ia supernovae explosions. We use the results of a parameter study of two-dimensional direct numerical simulations of an RT unstable model flame to distinguish between the two main types of subgrid models (RT or turbulence dominated) in the flamelet regime. First, we give scalings for the turbulent flame speed, the Reynolds number, the viscous scale, and the size of the burning region as the non-dimensional gravity (G) is varied. The flame speed is well predicted by an RT-based flame speed model. Next, the above scalings are used to calculate the Karlovitz number (Ka) and to discuss appropriate combustion regimes. No transition to thin reaction zones is seen at Ka = 1, although such a transition is expected by turbulence-dominated subgrid models. Finally, we confirm a basic physical premise of the RT subgrid model, namely, that the flame is fractal, and thus self-similar. By modeling the turbulent flame speed, we demonstrate that it is affected more by large-scale RT stretching than by small-scale turbulent wrinkling. In this way, the RT instability controls the flame directly from the large scales. Overall, these results support the RT subgrid model.

  15. Rayleigh-Taylor stabilization by material strength at Mbar pressures

    Energy Technology Data Exchange (ETDEWEB)

    Park, H; Lorenz, K T; Cavallo, R M; Pollaine, S M; Prisbrey, S T; Remington, B A; Rudd, R E; Becker, R C; Bernier, J V

    2009-05-27

    Studies of solid-state material dynamics at high pressures ({approx}1 Mbar) and ultrahigh strain rates (>10{sup 6} s{sup -1}) are performed using a unique laser based, quasi-isentropic high-pressure acceleration platform. Vanadium foils with pre-imposed sinusoidal ripples are accelerated in the solid state with this ramped high pressure drive. This causes Rayleigh-Taylor (RT) instability growth at the interface, where the rate of growth is sensitive to the solid-state material properties. The RT growth history is measured by face-on radiography using synchronized laser-driven x-ray backlighters at the Omega Laser. The experimental results are compared with 2D hydrodynamics simulations utilizing constitutive models of high pressure material strength. We find that the vanadium strength increases by a factor of 3.5-4 at peak pressure, compared to its ambient (undriven) strength. Both pressure hardening and strain rate hardening are the suggested cause for this increase in strength. An analysis treating strength as an effective lattice viscosity finds that a viscosity of {approx}400 poise is required to reproduce our RT data.

  16. Effects of thermal conduction and compressibility on Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Takabe, Hideaki; Mima, Kunioki.

    1980-01-01

    In order to study the stability of the ablation front in laser driven implosion, the thermal conduction and compressibility effects on the Rayleigh-Taylor instability are considered. It is found that the thermal conduction effect cannot stabilize the Rayleigh-Taylor mode, but reduce the growth rate in the short wavelength case. But, the growth rate is found not to differ from the classical value √gk in the long wavelength limit, where the compressibility is essential. (author)

  17. Prominence Bubble Shear Flows and the Coupled Kelvin-Helmholtz — Rayleigh-Taylor Instability

    Science.gov (United States)

    Berger, Thomas; Hillier, Andrew

    2017-08-01

    Prominence bubbles are large arched structures that rise from below into quiescent prominences, often growing to heights on the order of 10 Mm before going unstable and generating plume upflows. While there is general agreement that emerging flux below pre-existing prominences causes the structures, there is lack of agreement on the nature of the bubbles and the cause of the instability flows. One hypothesis is that the bubbles contain coronal temperature plasma and rise into the prominence above due to both magnetic and thermal buoyancy, eventually breaking down via a magnetic Rayleigh-Taylor (RT) instability to release hot plasma and magnetic flux and helicity into the overlying coronal flux rope. Another posits that the bubbles are actually just “arcades” in the prominence indicating a magnetic separator line between the bipole and the prominence fields with the observed upflows and downflows caused by reconnection along the separator. We analyze Hinode/SOT, SDO/AIA, and IRIS observations of prominence bubbles, focusing on characteristics of the bubble boundary layers that may discriminate between the two hypotheses. We find speeds on the order of 10 km/s in prominence plasma downflows and lateral shear flows along the bubble boundary. Inflows to the boundary gradually increase the thickness and brightness of the layer until plasma drains from there, apparently around the dome-like bubble domain. In one case, shear flow across the bubble boundary develops Kelvin-Helmholtz (KH) vortices that we use to infer flow speeds in the low-density bubble on the order of 100 km/sec. IRIS spectra indicate that plasma flows on the bubble boundary at transition region temperatures achieve Doppler speeds on the order of 50 km/s, consistent with this inference. Combined magnetic KH-RT instability analysis leads to flux density estimates of 10 G with a field angle of 30° to the prominence, consistent with vector magnetic field measurements. In contrast, we find no evidence

  18. Rayleigh-Taylor Instability Evolution in Ablatively Driven Cylindrical Implosions^*,**

    Science.gov (United States)

    Hsing, W. W.

    1996-11-01

    The Rayleigh-Taylor instability is an important limitation in ICF capsule designs. Significant work both theoretically and experimentally has been done to demonstrate the stabilizing effects due to material flow through the unstable region. The experimental verification has been done predominantly in planar geometry. Convergent geometry introduces effects not present in planar geometry such as shell thickening and accelerationless growth of modal amplitudes (e.g. Bell-Plesset growth). Amplitude thresholds for the nonlinear regime are reduced, since the wavelength of a mode m decreases with convergence λ ~ r/m, where r is the radius. We have investigated convergent effects using an imploding cylinder driven by x-ray ablation on the NOVA laser. By doping sections of the cylinder with high-Z materials, in conjunction with x-ray backlighting, we have measured the growth and feedthrough of the perturbations from the ablation front to the inner surface of the cylinder for various initial modes and amplitudes from early time through stagnation. Mode coupling of illumination asymmetries with material perturbations is observed, as well as phase reversal of the perturbations from near the ablation front to the inner surface of the cylinder. Imaging is performed with an x-ray pinhole camera coupled to a gated microchannel plate detector. In collaboration with C. W. Barnes, J. B. Beck, N. Hoffman (LANL), D. Galmiche, A. Richard (CEA/L-V), J. Edwards, P. Graham, B. Thomas (AWE). ^**This work was performed under the auspices of the U.S. Department of Energy by the Los Alamos National Laboratory under Contract No. W-7405-ENG-36.

  19. Roles of bulk viscosity on Rayleigh-Taylor instability: Non-equilibrium thermodynamics due to spatio-temporal pressure fronts

    Energy Technology Data Exchange (ETDEWEB)

    Sengupta, Tapan K., E-mail: tksen@iitk.ac.in; Bhole, Ashish; Shruti, K. S. [HPCL, Department of Aerospace Engineering, IIT Kanpur, Kanpur, UP (India); Sengupta, Aditi [Department of Engineering, University of Cambridge, Cambridge (United Kingdom); Sharma, Nidhi [Graduate Student, HPCL, Department of Aerospace Engineering, IIT Kanpur, Kanpur, UP (India); Sengupta, Soumyo [Department of Mechanical and Aerospace Engineering, Ohio State University, Columbus, Ohio 43210 (United States)

    2016-09-15

    Direct numerical simulations of Rayleigh-Taylor instability (RTI) between two air masses with a temperature difference of 70 K is presented using compressible Navier-Stokes formulation in a non-equilibrium thermodynamic framework. The two-dimensional flow is studied in an isolated box with non-periodic walls in both vertical and horizontal directions. The non-conducting interface separating the two air masses is impulsively removed at t = 0 (depicting a heaviside function). No external perturbation has been used at the interface to instigate the instability at the onset. Computations have been carried out for rectangular and square cross sections. The formulation is free of Boussinesq approximation commonly used in many Navier-Stokes formulations for RTI. Effect of Stokes’ hypothesis is quantified, by using models from acoustic attenuation measurement for the second coefficient of viscosity from two experiments. Effects of Stokes’ hypothesis on growth of mixing layer and evolution of total entropy for the Rayleigh-Taylor system are reported. The initial rate of growth is observed to be independent of Stokes’ hypothesis and the geometry of the box. Following this stage, growth rate is dependent on the geometry of the box and is sensitive to the model used. As a consequence of compressible formulation, we capture pressure wave-packets with associated reflection and rarefaction from the non-periodic walls. The pattern and frequency of reflections of pressure waves noted specifically at the initial stages are reflected in entropy variation of the system.

  20. Potential flow model for the hydromagnetic Rayleigh--Taylor instability in cylindrical plasmas

    International Nuclear Information System (INIS)

    Hwang, C.S.; Roderick, N.F.

    1987-01-01

    A potential flow model has been developed to study the linear behavior of the hydromagnetic equivalent of the Rayleigh--Taylor instability in imploding cylindrical plasmas. Ordinary differential equations are obtained for both (r,z) and (r,θ) disturbances. The model allows the study of the dynamic effects of the moving plasma on the development of the instability. The perturbation equations separate into a geometric part associated with the motion of the interface and a nongeometric part associated with the stability of the interface. In both planes the geometric part shows growth of perturbations for imploding plasmas. The surface is also unstable in both planes for plasmas being imploded by magnetic fields. Analytic solutions are obtained for constant acceleration. These show that the short wavelength perturbations that are most damaging in the (r,z) plane are not affected by the motion of the interface. In the (r,θ) plane the growth of longer wavelength disturbances is affected by the interface motion

  1. Experimental Studies of the Electrothermal and Magneto-Rayleigh Taylor Instabilities on Thin Metal Foil Ablations

    Science.gov (United States)

    Steiner, Adam; Yager-Elorriaga, David; Patel, Sonal; Jordan, Nicholas; Gilgenbach, Ronald; Lau, Y. Y.

    2015-11-01

    The electrothermal instability (ETI) and magneto-Rayleigh Taylor instability (MRT) are important in the implosion of metallic liners, such as magnetized liner implosion fusion (MagLIF). The MAIZE linear transformer driver (LTD) at the University of Michigan generates 200 ns risetime-current pulses of 500 to 600 kA into Al foil liners to study plasma instabilities and implosion dynamics, most recently MRT growth on imploding cylindrical liners. A full circuit model of MAIZE, along with I-V measurements, yields time-resolved load inductance. This has enabled measurements of an effective current-carrying radius to determine implosion velocity and plasma-vacuum interface acceleration. Measurements are also compared to implosion data from 4-time-frame laser shadowgraphy. Improved resolution measurements on the laser shadowgraph system have been used to examine the liner interface early in the shot to examine surface perturbations resulting from ETI for various seeding conditions. Fourier analysis examines the growth rates of wavelength bands of these structures to examine the transition from ETI to MRT. This work was supported by the U.S. DoE through award DE-SC0012328. S.G. Patel is supported by Sandia National Labs. D.A. Yager is supported by NSF fellowship grant DGE 1256260.

  2. Magneto-Rayleigh-Taylor Instability Experimental Progress on Thin Foils Driven by a 1-MA LTD*

    Science.gov (United States)

    Zier, J. C.; Lau, Y. Y.; Gomez, M. R.; Tang, W. W.; Franzi, M. A.; French, D. M.; Gilgenbach, R. M.; Mazarakis, M. G.; Cuneo, M. E.; Lopez, M. R.; Oliver, B. V.; Mehlhorn, T. A.

    2009-11-01

    Foils may soon become necessary to achieve the required mass for higher current-driven x-ray sources. They may also offer useful options for x-ray pulse shaping and as imploding liners for magnetized target fusion. This paper reports our latest design and experimental progress on the dominant instability, the magneto-Rayleigh-Taylor instability (MRT). Planar Al foils as thin as 400 nm driven by the 1-MA linear transformer driver (LTD), MAIZE, at the U of Michigan, are used as the dynamic loads for this investigation. A higher inductance feed will be used to lengthen the current drive to achieve >10 e-foldings of MRT growth for observation with a laser backlighter. Inductance considerations, schlieren and interferometry diagnostics, and experimental progress will be presented along with MRT theory. *This work was supported by US DoE through Sandia National Labs award numbers 240985 and 76822 to the U of Michigan. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the US DoE's NNSA under Contract DE-AC04-94AL85000. JCZ was supported by a NPSC fellowship through Sandia National Labs. MRG was supported by a SSGF fellowship through NNSA.

  3. Stability of an expanding cylindrical plasma envelope: Rayleigh--Taylor instability

    International Nuclear Information System (INIS)

    Han, S.J.

    1982-01-01

    The stability of a cylindrically symmetric plasma envelope driven outward by blast waves is considered. The plasma fluid is assumed to be a compressible, isentropic gas describable as an ideal gas ( p = arho/sup γ/, γ>1). The stability problem of such an envelope undergoing self-similar motion is solved by considering the initial-value problem. It is shown that in the early phase of an expansion, the envelope is unstable to Rayleigh--Taylor modes which develop at the inner surface. In the later phase of the expansion, the Rayleigh--Taylor modes are weakened due to the geometrical divergence effect. The implications of the time-dependent behavior of the Rayleigh--Taylor instability for plasma switches are discussed

  4. Weakly nonlinear incompressible Rayleigh-Taylor instability growth at cylindrically convergent interfaces

    International Nuclear Information System (INIS)

    Wang, L. F.; He, X. T.; Wu, J. F.; Zhang, W. Y.; Ye, W. H.

    2013-01-01

    A weakly nonlinear (WN) model has been developed for the incompressible Rayleigh-Taylor instability (RTI) in cylindrical geometry. The transition from linear to nonlinear growth is analytically investigated via a third-order solutions for the cylindrical RTI initiated by a single-mode velocity perturbation. The third-order solutions can depict the early stage of the interface asymmetry due to the bubble-spike formation, as well as the saturation of the linear (exponential) growth of the fundamental mode. The WN results in planar RTI [Wang et al., Phys. Plasmas 19, 112706 (2012)] are recovered in the limit of high-mode number perturbations. The difference between the WN growth of the RTI in cylindrical geometry and in planar geometry is discussed. It is found that the interface of the inward (outward) development spike/bubble is extruded (stretched) by the additional inertial force in cylindrical geometry compared with that in planar geometry. For interfaces with small density ratios, the inward growth bubble can grow fast than the outward growth spike in cylindrical RTI. Moreover, a reduced formula is proposed to describe the WN growth of the RTI in cylindrical geometry with an acceptable precision, especially for small-amplitude perturbations. Using the reduced formula, the nonlinear saturation amplitude of the fundamental mode and the phases of the Fourier harmonics are studied. Thus, it should be included in applications where converging geometry effects play an important role, such as the supernova explosions and inertial confinement fusion implosions.

  5. Thin layer model for nonlinear evolution of the Rayleigh-Taylor instability

    Science.gov (United States)

    Zhao, K. G.; Wang, L. F.; Xue, C.; Ye, W. H.; Wu, J. F.; Ding, Y. K.; Zhang, W. Y.

    2018-03-01

    On the basis of the thin layer approximation [Ott, Phys. Rev. Lett. 29, 1429 (1972)], a revised thin layer model for incompressible Rayleigh-Taylor instability has been developed to describe the deformation and nonlinear evolution of the perturbed interface. The differential equations for motion are obtained by analyzing the forces (the gravity and pressure difference) of fluid elements (i.e., Newton's second law). The positions of the perturbed interface are obtained from the numerical solution of the motion equations. For the case of vacuum on both sides of the layer, the positions of the upper and lower interfaces obtained from the revised thin layer approximation agree with that from the weakly nonlinear (WN) model of a finite-thickness fluid layer [Wang et al., Phys. Plasmas 21, 122710 (2014)]. For the case considering the fluids on both sides of the layer, the bubble-spike amplitude from the revised thin layer model agrees with that from the WN model [Wang et al., Phys. Plasmas 17, 052305 (2010)] and the expanded Layzer's theory [Goncharov, Phys. Rev. Lett. 88, 134502 (2002)] in the early nonlinear growth regime. Note that the revised thin layer model can be applied to investigate the perturbation growth at arbitrary Atwood numbers. In addition, the large deformation (the large perturbed amplitude and the arbitrary perturbed distributions) in the initial stage can also be described by the present model.

  6. Discrete Boltzmann modeling of Rayleigh-Taylor instability in two-component compressible flows

    Science.gov (United States)

    Lin, Chuandong; Xu, Aiguo; Zhang, Guangcai; Luo, Kai Hong; Li, Yingjun

    2017-11-01

    A discrete Boltzmann model (DBM) is proposed to probe the Rayleigh-Taylor instability (RTI) in two-component compressible flows. Each species has a flexible specific-heat ratio and is described by one discrete Boltzmann equation (DBE). Independent discrete velocities are adopted for the two DBEs. The collision and force terms in the DBE account for the molecular collision and external force, respectively. Two types of force terms are exploited. In addition to recovering the modified Navier-Stokes equations in the hydrodynamic limit, the DBM has the capability of capturing detailed nonequilibrium effects. Furthermore, we use the DBM to investigate the dynamic process of the RTI. The invariants of tensors for nonequilibrium effects are presented and studied. For low Reynolds numbers, both global nonequilibrium manifestations and the growth rate of the entropy of mixing show three stages (i.e., the reducing, increasing, and then decreasing trends) in the evolution of the RTI. On the other hand, the early reducing tendency is suppressed and even eliminated for high Reynolds numbers. Relevant physical mechanisms are analyzed and discussed.

  7. Observation of Rayleigh-Taylor-like structures in a laser-accelerated foil

    International Nuclear Information System (INIS)

    Whitlock, R.R.; Emery, M.H.; Stamper, J.A.; McLean, E.A.; Obenschain, S.P.; Peckerar, M.C.

    1984-01-01

    Laser-accelerated targets have been predicted to be subject to the Rayleigh-Taylor hydrodynamic instability. The development of the instability was studied by introducing mass thickness variations in foil targets and observing the development of the target nonuniformities by side-on flash x radiography. Observations were made of target structures and mass redistribution effects which resemble Rayleigh-Taylor bubbles and spikes, including not only advanced broadening of the spike tips on the laser-irradiated side of the foil but also projections of mass on the unirradiated side. The observations compare well with numerical simulations

  8. Observation of the stabilizing effect of a laminated ablator on the ablative Rayleigh-Taylor instability.

    Science.gov (United States)

    Masse, L; Casner, A; Galmiche, D; Huser, G; Liberatore, S; Theobald, M

    2011-05-01

    A laminated ablator is explored as an alternative concept for stabilizing the ablative Rayleigh-Taylor instability which develops in inertial fusion targets. Experiments measuring the growth of the Rayleigh-Taylor instability of laminated planar foils are reported. Consistent with both theory and simulations, a significant reduction of the perturbation growth is experimentally observed for laminated ablators in comparison to what is observed for classical uniform ablators. Such an enhanced hydrodynamic stability opens opportunities for the design of high-gain inertial fusion targets. © 2011 American Physical Society

  9. Measurement of the Rayleigh-Taylor instability in targets driven by optically smoothed laser beams

    International Nuclear Information System (INIS)

    Desselberger, M.; Willi, O.; Savage, M.; Lamb, M.J.

    1990-01-01

    Growth rates of the Rayleigh-Taylor instability were measured in targets with imposed sinusoidal modulations irradiated by optically smoothed 0.53-μm laser beams. A hybrid optical smoothing technique utilizing induced-spatial-incoherence and random-phase-plate technology was used for the first time. The wave-number dependence and the nonlinear behavior of Rayleigh-Taylor growth were investigated by using targets with a range of modulation periodicities and depths. The results are compared to 2D hydrodynamic-code simulations

  10. Suppression of the Rayleigh-Taylor instability due to self-radiation in a multiablation target

    International Nuclear Information System (INIS)

    Fujioka, Shinsuke; Sunahara, Atsushi; Nishihara, Katsunobu; Johzaki, Tomoyuki; Shiraga, Hiroyuki; Shigemori, Keisuke; Nakai, Mitsuo; Ikegawa, Tadashi; Murakami, Masakatsu; Nagai, Keiji; Norimatsu, Takayoshi; Azechi, Hiroshi; Yamanaka, Tatsuhiko; Ohnishi, Naofumi

    2004-01-01

    A scheme to suppress the Rayleigh-Taylor instability has been investigated for a direct-drive inertial fusion target. In a high-Z doped-plastic target, two ablation surfaces are formed separately--one driven by thermal radiation and the other driven by electron conduction. The growth of the Rayleigh-Taylor instability is significantly suppressed on the radiation-driven ablation surface inside the target due to the large ablation velocity and long density scale length. A significant reduction of the growth rate was observed in simulations and experiments using a brominated plastic target. A new direct-drive pellet was designed using this scheme

  11. Hybrid simulations of radial transport driven by the Rayleigh-Taylor instability

    Science.gov (United States)

    Delamere, P. A.; Stauffer, B. H.; Ma, X.

    2017-12-01

    Plasma transport in the rapidly rotating giant magnetospheres is thought to involve a centrifugally-driven flux tube interchange instability, similar to the Rayleigh-Taylor (RT) instability. In three dimensions, the convective flow patterns associated with the RT instability can produce strong guide field reconnection, allowing plasma mass to move radially outward while conserving magnetic flux (Ma et al., 2016). We present a set of hybrid (kinetic ion / fluid electron) plasma simulations of the RT instability using high plasma beta conditions appropriate for Jupiter's inner and middle magnetosphere. A density gradient, combined with a centrifugal force, provide appropriate RT onset conditions. Pressure balance is achieved by initializing two ion populations: one with fixed temperature, but varying density, and the other with fixed density, but a temperature gradient that offsets the density gradient from the first population and the centrifugal force (effective gravity). We first analyze two-dimensional results for the plane perpendicular to the magnetic field by comparing growth rates as a function of wave vector following Huba et al. (1998). Prescribed perpendicular wave modes are seeded with an initial velocity perturbation. We then extend the model to three dimensions, introducing a stabilizing parallel wave vector. Boundary conditions in the parallel direction prohibit motion of the magnetic field line footprints to model the eigenmodes of the magnetodisc's resonant cavity. We again compare growth rates based on perpendicular wave number, but also on the parallel extent of the resonant cavity, which fixes the size of the largest parallel wavelength. Finally, we search for evidence of strong guide field magnetic reconnection within the domain by identifying areas with large parallel electric fields or changes in magnetic field topology.

  12. A numerical study of the nonlinear Rayleigh-Taylor instability, with application of accreting X-ray sources

    International Nuclear Information System (INIS)

    Wang, Y.M.; Nepveu, M.

    1983-01-01

    With a view toward applications to accreting X-ray sources, the Rayleigh-Taylor instability is followed numerically, using a 2-D magnetohydrodynamic code. The presence of a uniform magnetic field in the underlying medium is allowed for. The infalling plasma is found to develop elongated, trailing loops; at least when the initial perturbation is highly symmetric, a narrow neck also forms through the action of the surrounding ram pressure. It is suggested that the swirling motion present in the nonlinear phase could produce some effective large-scale mixing between accreting plasma and the magnetospheric field of a neutron star. Another potentially significant tendency is for the curvature of the infalling plasma pocket to sharpen as the instability develops: magnetic tension may therefore become increasingly effective as a stabilizing influence. (orig.)

  13. Self-consistent model of the Rayleigh--Taylor instability in ablatively accelerated laser plasma

    International Nuclear Information System (INIS)

    Bychkov, V.V.; Golberg, S.M.; Liberman, M.A.

    1994-01-01

    A self-consistent approach to the problem of the growth rate of the Rayleigh--Taylor instability in laser accelerated targets is developed. The analytical solution of the problem is obtained by solving the complete system of the hydrodynamical equations which include both thermal conductivity and energy release due to absorption of the laser light. The developed theory provides a rigorous justification for the supplementary boundary condition in the limiting case of the discontinuity model. An analysis of the suppression of the Rayleigh--Taylor instability by the ablation flow is done and it is found that there is a good agreement between the obtained solution and the approximate formula σ = 0.9√gk - 3u 1 k, where g is the acceleration, u 1 is the ablation velocity. This paper discusses different regimes of the ablative stabilization and compares them with previous analytical and numerical works

  14. Evidence of Rayleigh-Taylor instabilities in tri-layer targets

    International Nuclear Information System (INIS)

    Galmiche, D.; Holstein, P.A.; Meyer, B.; Rostaing, M.; Wilke, N.

    1988-01-01

    The results of the experiments carried out on a laser system are reported. The work is performed in order to investigate the problem of target instability under ablative acceleration and to get direct evidence of Rayleigh-Taylor instabilities. Tri-layer experiments assert the validity of X-ray spectroscopy measurements as experimental method to investigate the problem. A mixing zone is evidenced and general trends of mixing development versus target acceleration are coherent with numerical simulations. Results obtained with optical smoothing demonstrate that the apparent mixing is not due to large scale illumination non uniformities. Numerical simulations confirm that Rayleigh-Taylor instability seems to be the dominant process responsible for the mixing. Benefit of time resolved spectroscopy appears attractive and gives a real knowledge of the mixing layer

  15. Designs for highly nonlinear ablative Rayleigh-Taylor experiments on the National Ignition Facility

    International Nuclear Information System (INIS)

    Casner, A.; Masse, L.; Liberatore, S.; Jacquet, L.; Loiseau, P.; Poujade, O.; Smalyuk, V. A.; Bradley, D. K.; Park, H. S.; Remington, B. A.; Igumenshchev, I.; Chicanne, C.

    2012-01-01

    We present two designs relevant to ablative Rayleigh-Taylor instability in transition from weakly nonlinear to highly nonlinear regimes at the National Ignition Facility [E. I. Moses, J. Phys.: Conf. Ser. 112, 012003 (2008)]. The sensitivity of nonlinear Rayleigh-Taylor instability physics to ablation velocity is addressed with targets driven by indirect drive, with stronger ablative stabilization, and by direct drive, with weaker ablative stabilization. The indirect drive design demonstrates the potential to reach a two-dimensional bubble-merger regime with a 20 ns duration drive at moderate radiation temperature. The direct drive design achieves a 3 to 5 times increased acceleration distance for the sample in comparison to previous experiments allowing at least 2 more bubble generations when starting from a three-dimensional broadband spectrum.

  16. Three-dimensional single-mode nonlinear ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Yan, R.; Aluie, H.; Betti, R.; Sanz, J.; Liu, B.; Frank, A.

    2016-01-01

    The nonlinear evolution of the single-mode ablative Rayleigh-Taylor instability is studied in three dimensions. As the mode wavelength approaches the cutoff of the linear spectrum (short-wavelength modes), it is found that the three-dimensional (3D) terminal bubble velocity greatly exceeds both the two-dimensional (2D) value and the classical 3D bubble velocity. Unlike in 2D, the 3D short-wavelength bubble velocity does not saturate. The growing 3D bubble acceleration is driven by the unbounded accumulation of vorticity inside the bubble. The vorticity is transferred by mass ablation from the Rayleigh-Taylor spikes to the ablated plasma filling the bubble volume

  17. The Rayleigh-Taylor instability in a self-gravitating two-layer viscous sphere

    Science.gov (United States)

    Mondal, Puskar; Korenaga, Jun

    2018-03-01

    The dispersion relation of the Rayleigh-Taylor instability in the spherical geometry is of profound importance in the context of the Earth's core formation. Here we present a complete derivation of this dispersion relation for a self-gravitating two-layer viscous sphere. Such relation is, however, obtained through the solution of a complex transcendental equation, and it is difficult to gain physical insights directly from the transcendental equation itself. We thus also derive an empirical formula to compute the growth rate, by combining the Monte Carlo sampling of the relevant model parameter space with linear regression. Our analysis indicates that the growth rate of Rayleigh-Taylor instability is most sensitive to the viscosity of inner layer in a physical setting that is most relevant to the core formation.

  18. Nonlinear spectrum of the ablative Rayleigh-Taylor instability in laser-accelerated planar plasmas

    International Nuclear Information System (INIS)

    Keskinen, M. J.; Schmitt, A.

    2007-01-01

    A model for the nonlinear spectrum of the ablative Rayleigh-Taylor instability in laser-accelerated planar plasmas has been developed for a wide range of Froude numbers and scale sizes. It is found that the spectrum can be characterized by an inverse power law with spectral index of approximately 2 in the limit of small-wavenumber spectrum cutoffs and small-scale density gradient scale lengths. Comparison of the model spectrum with recent experimental observations is made with good agreement

  19. Rayleigh-Taylor instability of a self-similar spherical expansion

    International Nuclear Information System (INIS)

    Bernstein, I.B.; Book, D.L.

    1978-01-01

    The self-similar motion of a spherically symmetric isentropic cloud of ideal gas driven outward by an expanding low-density medium (e.g., radiation pressure from a pulsar) is shown to be unstable to Rayleigh-Taylor modes which develop in the neighborhood of the interface. A complete solution of the linearized equations of motion is obtained. The implications for astrophysical phenomena are discussed

  20. Three-dimensional, nonlinear evolution of the Rayleigh--Taylor instability of a thin layer

    International Nuclear Information System (INIS)

    Manheimer, W.; Colombant, D.; Ott, E.

    1984-01-01

    A numerical simulation scheme is developed to examine the nonlinear evolution of the Rayleigh--Taylor instability of a thin sheet in three dimensions. It is shown that the erosion of mass at the top of the bubble is approximately as described by two-dimensional simulations. However, mass is lost into spikes more slowly in three-dimensional than in two-dimensional simulations

  1. Mechanism of growth reduction of the deceleration-phase ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Atzeni, Stefano; Temporal, Mauro

    2003-01-01

    The deceleration-phase (dp) ablative Rayleigh-Taylor instability (RTI) of igniting and nonigniting inertial fusion capsules is studied by high-resolution two-dimensional Lagrangian fluid simulations. It is found that growth reduction of the dp-RTI with respect to classical RTI results from the advection of perturbed fluid elements outside a thin unstable fluid layer. Within this layer, at fixed Lagrangian position, perturbations grow approximately classically

  2. Breakup of an accelerated shell owing to Rayleigh--Taylor instability

    International Nuclear Information System (INIS)

    Suydam, B.R.

    1978-06-01

    A simplified model for the Rayleigh-Taylor instability of an accelerated shell is examined, and it is found that the most dangerous wavelength to be about that of the shell thickness. The shell material is assumed to be an inviscid, incompressible fluid. Effects of finite compressibility and of surface tension are found to be negligible, but the effects of viscosity are shown to be very large. The need for better knowledge of viscosity at high pressure is pointed out

  3. Combined effect of viscosity and vorticity on single mode Rayleigh-Taylor instability bubble growth

    International Nuclear Information System (INIS)

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

    2011-01-01

    The combined effect of viscosity and vorticity on the growth rate of the bubble associated with single mode Rayleigh-Taylor instability is investigated. It is shown that the effect of viscosity on the motion of the lighter fluid associated with vorticity accumulated inside the bubble due to mass ablation may be such as to reduce the net viscous drag on the bubble exerted by the upper heavier fluid as the former rises through it.

  4. Numerical simulation of Rayleigh-Taylor instability in ablation driven systems

    International Nuclear Information System (INIS)

    Verdon, C.P.

    1984-01-01

    Two-dimensional numerical simulations of ablatively accelerated thin shells subject to Rayleigh-Taylor instability are presented. Results for both single wavelength and multiwavelength perturbations show that the nonlinear effects of the instability are evident mainly in the bubble rather than the spike. Approximate roles for predicting the dominant nonlinear mode-mode interactions, which limit shell performance, are also discussed. The work concludes with a discussion of recommendations for future work in this area

  5. Three-dimensional simulations of the Rayleigh-Taylor instability during the deceleration phase

    International Nuclear Information System (INIS)

    Town, R.P.J.; Jones, B.J.; Findlay, J.D.; Bell, A.R.

    1994-01-01

    The growth of the Rayleigh-Taylor instability in three dimensions is examined during the deceleration phase of an inertial confinement fusion implosion. A detailed discussion of the three-dimensional hydrocode, PLATO, is presented. A review of previous calculations is given, concentrating on the shape of the R-T instability in three dimensions. Results of the growth rate during the linear phase, the saturation amplitude, and the nonlinear evolution are presented. (Author)

  6. Rayleigh-Taylor instabilities in indirect laser drive with rugby-shaped hohlraums; Experiences d'instabilites Rayleigh-Taylor en attaque indirecte avec des cavites rugby

    Energy Technology Data Exchange (ETDEWEB)

    Casner, A.; Galmiche, D.; Huser, G.; Jadaud, J.P.; Richard, A.; Liberatore, S.; Vandenboomgaerde, M. [CEA Bruyeres-le-Chatel, 91 (France)

    2009-07-01

    The mastering of the development of hydrodynamic instabilities like Rayleigh-Taylor instabilities is an important milestone on the way to perform efficient laser implosions. The complexity of these instabilities implies an experimental validation of the theoretical models and their computer simulations. An experimental platform involving the Omega laser has allowed us to perform indirect drive with rugby-shaped hohlraums. The experiments have validated the growth of 2- and 3-dimensional initial defects as predicted by theory. We have shown that the 3-dimensional defect saturates for an higher amplitude than the 2-dimensional one does. The experiments have been made by using a plastic shell doped with Germanium (CH:Ge). (A.C.)

  7. Contribution to modelization and simulation of the ablative-like Rayleigh-Taylor instabilities for ICF; Contribution a la modelisation et a la simulation des instabilites de type Rayleigh-Taylor ablatif pour la FCI

    Energy Technology Data Exchange (ETDEWEB)

    Egly, H

    2007-10-15

    This thesis deals with the dynamics of accelerated ablative front spreading in Inertial Confinement Fusion experiments. ICF is designed for the implosion of a deuterium-tritium spherical target. The outer shell, the ablator, is irradiated providing a high level pressure inside the target. During this first stage, the ablation front propagating inwards is perturbed by hydrodynamics instabilities, which can prevent the fusion reaction in the decelerated stage. We propose here a study on Rayleigh-Taylor instabilities during ablation process, in the two dimensional case. In order to obtain a numerical solution, we perform an asymptotic analysis in the limit of a high temperature ratio, between the remaining cold ablator and the hot ablated plasma. This study is divided in two steps. First, the thermo-diffusive part of the set of equations is approximated by a Hele-Shaw model, which is then perturbed by the hydrodynamics part. Using a vortex method, we have to solve the advection of a vortical sheet moving with the ablation front. We compute the numerical solution on an Eulerian mesh coupled with a marker method. The thermal part is computed by implementing the Fat Boundary Method, recently developed. The hydrodynamic part is obtained from a Finite Volume scheme. (author)

  8. The Rayleigh-Taylor instability under electrical pulse discharge in water

    International Nuclear Information System (INIS)

    Kononov, A.V.; Porytskyy, P.V.; Starchyk, P.D.; Voitenko, L.M.

    1999-01-01

    The development of the Rayleigh-Taylor instability is studied on the interface between both the plasma channel and liquid medium under an electrical pulse discharge in water.It is shown that,growth of the irregularities of the contact interface leads to the increasing of heat flux from the discharge channel due to the growth of an interfacial area and the incoming of water matter into a discharge channel.As a result of these processes the characteristics of the discharge may be strongly varied

  9. Initial value problem for Rayleigh--Taylor instability of viscous fluids

    International Nuclear Information System (INIS)

    Menikoff, R.; Mjolsness, R.C.; Sharp, D.H.; Zemach, C.; Doyle, B.J.

    1978-01-01

    The initial value problem associated with the development of small amplitude disturbances in Rayleigh--Taylor unstable, viscous, incompressible fluids is studied. Solutions to the linearized equations of motion which satisfy general initial conditions are obtained in terms of Fourier--Laplace transforms of the hydrodynamic variables, without restriction on the density or viscosity of either fluid. When the two fluids have equal kinematic viscosities, these transforms can be inverted explicitly to express the fluid variables as integrals of Green's functions multiplied by initial data. In addition to normal modes, a set of continuum modes, not treated explicitly in the literature, makes an important contribution to the development of the fluid motion

  10. Rayleigh-Taylor and Kelvin-Helmholtz instabilities in targets accelerated by laser ablation

    International Nuclear Information System (INIS)

    Emery, M.H.; Gardner, J.H.; Boris, J.P.

    1982-01-01

    With use of the fast2d laser-shell model, the acceleration of a 20-μm-thick plastic foil up to 160 km/s has been simulated. It is possible to follow the Rayleigh-Taylor bubble-and-spike development far into the nonlinear regime and beyond the point of foil fragmentation. Strong shear flow develops which evolves into the Kelvin-Helmholtz instability. The Kelvin-Helmholtz instability causes the tips of the spikes to widen and as a result reduce their rate of ''fall.''

  11. Comprehensive numerical methodology for direct numerical simulations of compressible Rayleigh-Taylor instability

    Energy Technology Data Exchange (ETDEWEB)

    Reckinger, Scott James [Montana State Univ., Bozeman, MT (United States); Livescu, Daniel [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Vasilyev, Oleg V. [Univ. of Colorado, Boulder, CO (United States)

    2016-09-02

    A comprehensive numerical methodology has been developed that handles the challenges introduced by considering the compressive nature of Rayleigh-Taylor instability (RTI) systems, which include sharp interfacial density gradients on strongly stratified background states, acoustic wave generation and removal at computational boundaries, and stratification-dependent vorticity production. The computational framework is used to simulate two-dimensional single-mode RTI to extreme late-times for a wide range of flow compressibility and variable density effects. The results show that flow compressibility acts to reduce the growth of RTI for low Atwood numbers, as predicted from linear stability analysis.

  12. Strong stabilization of the Rayleigh-Taylor instability by material strength at Mbar pressures

    Energy Technology Data Exchange (ETDEWEB)

    Park, H S; Lorenz, K T; Cavallo, R M; Pollaine, S M; Prisbrey, S T; Rudd, R E; Becker, R C; Bernier, J V; Remington, B A

    2009-11-19

    Experimental results showing significant reductions from classical in the Rayleigh-Taylor (RT) instability growth rate due to high pressure effective lattice viscosity are presented. Using a laser created ramped drive, vanadium samples are compressed and accelerated quasi-isentropically at {approx}1 Mbar pressures, while maintaining the sample in the solid-state. Comparisons with simulations and theory indicate that the high pressure, high strain rate conditions trigger a phonon drag mechanism, resulting in the observed high effective lattice viscosity and strong stabilization of the RT instability.

  13. Ablative Rayleigh-Taylor instability in the limit of an infinitely large density ratio

    International Nuclear Information System (INIS)

    Clavin, P.; Almarcha, Ch.

    2005-01-01

    The instability of ablation fronts strongly accelerated toward the dense medium under the conditions of inertial confinement fusion (ICF) is addressed in the limit of an infinitely large density ratio. The analysis serves to demonstrate that the flow is irrotational to first order, reducing the nonlinear analysis to solve a two-potential flows problem. Vorticity appears at the following orders in the perturbation analysis. This result simplifies greatly the analysis. The possibility for using boundary integral methods opens new perspectives in the nonlinear theory of the ablative Rayleigh-Taylor instability in ICF. A few examples are given at the end of the paper. (authors)

  14. Revisiting the Effects of Compressibility on the Rayleigh-Taylor Instability

    International Nuclear Information System (INIS)

    Zhou Qianhong; Li Ding

    2007-01-01

    The effects of compressibility on the Rayleigh-Taylor instability (RTI) are investigated. It is shown that the controversy over compressibility effects in the previous studies is due to improper comparison, in which the density varying effect obscures the real role of compressibility. After eliminating the density varying effect, it is found that the compressibility destabilizes RTI in both the cases of constant density and exponentially varying density when M T or greater values of gravity g, and the increment in the growth rate produced by compressibility depends inversely on the pressure p or the ratio of specific heat Γ

  15. Simple model of the Rayleigh-Taylor instability, collapse, and structural elements

    Science.gov (United States)

    Goncharov, V. P.; Pavlov, V. I.

    2013-08-01

    The mechanisms and structural elements of the Rayleigh-Taylor instability whose evolution results in the occurrence of the collapse have been studied in the scope of the rotating shallow water model with horizontal density gradient. Analysis of the instability mechanism shows that two collapse scenarios are possible. One scenario implies anisotropic collapse during which the contact area of a collapsing fragment with the bottom contracts into a spinning segment. The other implies isotropic contracting of the area into a point. The rigorous integral criteria and power laws of collapses are found.

  16. Proton Beam Fast Ignition Fusion: Synergy of Weibel and Rayleigh-Taylor Instabilities

    Science.gov (United States)

    Stefan, V. Alexander

    2011-04-01

    The proton beam generation and focusing in fast ignition inertial confinement fusion is studied. The spatial and energy spread of the proton beam generated in a laser-solid interaction is increased due to the synergy of Weibel and Rayleigh-Taylor instabilities. The focal spot radius can reach 100 μm, which is nearly an order of magnitude larger than the optimal value. The energy spread decreases the beam deposition energy in the focal spot. Under these conditions, ignition of a precompressed DT fuel is achieved with the beam powers much higher than the values presently in consideration. Work supported in part by NIKOLA TESLA Laboratories (Stefan University), La Jolla, CA.

  17. Analysis of weakly nonlinear three-dimensional Rayleigh--Taylor instability growth

    International Nuclear Information System (INIS)

    Dunning, M.J.; Haan, S.W.

    1995-01-01

    Understanding the Rayleigh--Taylor instability, which develops at an interface where a low density fluid pushes and accelerates a higher density fluid, is important to the design, analysis, and ultimate performance of inertial confinement fusion targets. Existing experimental results measuring the growth of two-dimensional (2-D) perturbations (perturbations translationally invariant in one transverse direction) are adequately modeled using the 2-D hydrodynamic code LASNEX [G. B. Zimmerman and W. L. Kruer, Comments Plasma Phys. Controlled Fusion 11, 51 (1975)]. However, of ultimate interest is the growth of three-dimensional (3-D) perturbations such as those initiated by surface imperfections or illumination nonuniformities. Direct simulation of such 3-D experiments with all the significant physical processes included and with sufficient resolution is very difficult. This paper addresses how such experiments might be modeled. A model is considered that couples 2-D linear regime hydrodynamic code results with an analytic model to allow modeling of 3-D Rayleigh--Taylor growth through the linear regime and into the weakly nonlinear regime. The model is evaluated in 2-D by comparison with LASNEX results. Finally the model is applied to estimate the dynamics of a hypothetical 3-D foil

  18. Method of generalized coordinates and an application to Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Dienes, J.K.

    1978-01-01

    The method of generalized coordinates is extended to the analysis of continuous bodies for which the degrees of freedom are independent velocity distributions in the spatial coordinates. The corresponding Lagrange equations contain generalized convective terms as well as the usual generalized forces and masses. Since the existence of a potential is not assumed, the equations of motion can be applied to media with arbitrary (possible dissipative) constitutive laws. Material deformation is characterized by the rate of strain, which is taken as the symmetric part of the velocity gradient, making the approach valid for arbitrarily large deformations. As an example, infinitesimal Rayleigh-Taylor instability is considered by analytic methods. Then, large amplitude Rayleigh-Taylor instability is represented with a single-degree-of-freedom analysis that shows the development (by numerical integration) of the known spike-and-bubble configuration of the unstable interface. The infinitesimal stability of a plastically deforming solid and the growth of the instability to large amplitudes are also considered

  19. Ablative stabilization of the Rayleigh-Taylor instability in regimes relevant to inertial confinement fusion

    Energy Technology Data Exchange (ETDEWEB)

    Kilkenny, J.D.

    1994-08-04

    As shown elsewhere an ablatively imploded shell is hydrodynamically unstable, the dominant instability being the well known Rayleigh-Taylor instability with growth rate {gamma} = {radical}Akg where k = 2{pi}/{lambda} is the wave number, g is the acceleration and A the Attwood number ({rho}{sub hi} {minus} {rho}{sub lo})/({rho}{sub hi} + {rho}{sub lo}) where {rho}{sub hi} is the density of the heavier fluid and {rho}{sub lo} is the density of the lighter fluid. A theoretical understanding of ablative stabilization has gradually evolved, confirmed over the last five years by experiments. The linear growth is very well understood with excellent agreement between experiment and simulation for planar geometry with wavelengths in the region of 30--100{mu}m. There is an accurate, albeit phenomenological dispersion relation. The non-linear growth has been measured and agrees with calculations. In this lecture, the authors go into the fundamentals of the Rayleigh-Taylor instability and the experimental measurements that show it is stabilized sufficiently by ablation in regimes relevant to ICF.

  20. Self-similarity in high Atwood number Rayleigh-Taylor experiments

    Science.gov (United States)

    Mikhaeil, Mark; Suchandra, Prasoon; Pathikonda, Gokul; Ranjan, Devesh

    2017-11-01

    Self-similarity is a critical concept in turbulent and mixing flows. In the Rayleigh-Taylor instability, theory and simulations have shown that the flow exhibits properties of self-similarity as the mixing Reynolds number exceeds 20000 and the flow enters the turbulent regime. Here, we present results from the first large Atwood number (0.7) Rayleigh-Taylor experimental campaign for mixing Reynolds number beyond 20000 in an effort to characterize the self-similar nature of the instability. Experiments are performed in a statistically steady gas tunnel facility, allowing for the evaluation of turbulence statistics. A visualization diagnostic is used to study the evolution of the mixing width as the instability grows. This allows for computation of the instability growth rate. For the first time in such a facility, stereoscopic particle image velocimetry is used to resolve three-component velocity information in a plane. Velocity means, fluctuations, and correlations are considered as well as their appropriate scaling. Probability density functions of velocity fields, energy spectra, and higher-order statistics are also presented. The energy budget of the flow is described, including the ratio of the kinetic energy to the released potential energy. This work was supported by the DOE-NNSA SSAA Grant DE-NA0002922.

  1. Study of three-dimensional Rayleigh--Taylor instability in compressible fluids through level set method and parallel computation

    International Nuclear Information System (INIS)

    Li, X.L.

    1993-01-01

    Computation of three-dimensional (3-D) Rayleigh--Taylor instability in compressible fluids is performed on a MIMD computer. A second-order TVD scheme is applied with a fully parallelized algorithm to the 3-D Euler equations. The computational program is implemented for a 3-D study of bubble evolution in the Rayleigh--Taylor instability with varying bubble aspect ratio and for large-scale simulation of a 3-D random fluid interface. The numerical solution is compared with the experimental results by Taylor

  2. What is certain and what is not so certain in our knowledge of Rayleigh-Taylor mixing?

    International Nuclear Information System (INIS)

    Anisimov, Sergei I.; Drake, R. Paul; Gauthier, Serge; Meshkov, Evgeny E.; Abarzhi, Snezhana I.

    2013-01-01

    Past decades significantly advanced our understanding of Rayleigh-Taylor (RT) mixing. We briefly review recent theoretical results and numerical modelling approaches and compare them with state of the art experiments focusing the reader's attention on qualitative properties of RT mixing. (authors)

  3. Stabilization of the Rayleigh - Taylor instability with convection in an ablatively accelerated laser plasma

    International Nuclear Information System (INIS)

    Bud'ko, A.B.; Liberman, M.A.

    1992-01-01

    In the framework of WKB approximation the problem is studied of stabilizing the Rayleigh - Taylor instability with unhomogeneous convective flow, developing in the ablation zone during the ablative acceleration of the laser target plasma. The eigenvalue (instability growth rates) problem is reduced to solving an algebraic equation with the coefficients depending on the unperturbed profile structure of hydrodynamic variables. For the important case of the incompressible plasma subsonic flow, the instability growth rates is shown to vanish at k=k 0 =max(2(g|∇ ln p|) 1/2 /ν). The consistency condition of the model consists in the smallness of the local Froude number in the region of instability development. However, as seen from the comparison with the numerical calculations, the model is well appicable also for the case of the sufficiently abrupt density gradient provided the Froude number is of order of unity

  4. 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)

  5. Rayleigh-Taylor growth measurements of three-dimensional modulations in a nonlinear regime

    International Nuclear Information System (INIS)

    Smalyuk, V.A.; Sadot, O.; Betti, R.; Goncharov, V.N.; Delettrez, J.A.; Meyerhofer, D.D.; Regan, S.P.; Sangster, T.C.; Shvarts, D.

    2006-01-01

    An understanding of the nonlinear evolution of Rayleigh-Taylor (RT) instability is essential in inertial confinement fusion and astrophysics. The nonlinear RT growth of three-dimensional (3-D) broadband nonuniformities was measured near saturation levels using x-ray radiography in planar foils accelerated by laser light. The initial 3-D target modulations were seeded by laser nonuniformities and subsequently amplified by the RT instability. The measured modulation Fourier spectra and nonlinear growth velocities are in excellent agreement with those predicted by Haan's model [S. Haan, Phys. Rev. A 39, 5812 (1989)]. These spectra and growth velocities are insensitive to initial conditions. In a real-space analysis, the bubble merger was quantified by a self-similar evolution of bubble size distributions, in agreement with the Alon-Oron-Shvarts theoretical predictions [D. Oron et al. Phys. Plasmas 8, 2883 (2001)

  6. Dynamics of Rayleigh-Taylor driven flows at high Atwood numbers

    Science.gov (United States)

    Mikhaeil, Mark; Akula, Bhanesh; Finn, Thomas; Ranjan, Devesh

    2014-11-01

    For the first time, detailed simultaneous density and velocity turbulent statistics for Rayleigh-Taylor instabilities at Atwood number of 0.75 are measured. A new density probe capable of measuring gas volumetric concentration directly is used in parallel to a three-wire probe to obtain instantaneous density and velocity components simultaneously. Particle Image Velocimetry (PIV) is also implemented to obtain field-wise measurements. The self-similarity behavior of the velocity statistics, corresponding probability density function (PDF) and spectra are presented. Mie-scattering images taken in both stream-wise and span-wise direction at different instability times have illustrated the turbulent structures visible in the instability. This work is graciously supported by DOE-National Nuclear Security Administration Grant Number DE-NA0001786.

  7. Design for solid-state Rayleigh-Taylor experiments in tantalum at Omega

    International Nuclear Information System (INIS)

    Pollaine, S M; Remington, B A; Park, H S; Prisbrey, S T; Cavallo, R M

    2010-01-01

    We have designed an experiment for the Omega - EP laser facility to measure the Rayleigh-Taylor (RT) growth rate of solid-state Ta samples at ∼1 Mbar pressures and very high strain rates, 10 7 -10 8 s -1 . A thin walled, hohlraum based, ramp-wave, quasi-isentropic drive has been developed for this experiment. Thick samples (∼50 um) of Ta, with a pre-imposed sinusoidal rippled on the driven side, will be accelerated. The ripple growth due to the RT instability is greatly reduced due to the dynamic material strength. We will show detailed designs, and a thorough error analysis used to optimize the experiment and minimize uncertainty.

  8. Jet-like long spike in nonlinear evolution of ablative Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Ye Wenhua; He Xiantu; Wang Lifeng

    2010-01-01

    We report the formation of jet-like long spike in the nonlinear evolution of the ablative Rayleigh-Taylor instability (ARTI) experiments by numerical simulations. A preheating model κ(T) = κ SH [1 + f(T)], where κ SH is the Spitzer-Haerm (SH) electron conductivity and f(T) interprets the preheating tongue effect in the cold plasma ahead of the ablative front [Phys. Rev. E 65 (2002) 57401], is introduced in simulations. The simulation results of the nonlinear evolution of the ARTI are in general agreement with the experiment results. It is found that two factors, i.e., the suppressing of ablative Kelvin-Helmholtz instability (AKHI) and the heat flow cone in the spike tips, contribute to the formation of jet-like long spike in the nonlinear evolution of the ARTI. (authors)

  9. Observation of Self-Similar Behavior of the 3D, Nonlinear Rayleigh-Taylor Instability

    International Nuclear Information System (INIS)

    Sadot, O.; Smalyuk, V.A.; Delettrez, J.A.; Sangster, T.C.; Goncharov, V.N.; Meyerhofer, D.D.; Betti, R.; Shvarts, D.

    2005-01-01

    The Rayleigh-Taylor unstable growth of laser-seeded, 3D broadband perturbations was experimentally measured in the laser-accelerated, planar plastic foils. The first experimental observation showing the self-similar behavior of the bubble size and amplitude distributions under ablative conditions is presented. In the nonlinear regime, the modulation σ rms grows as α σ gt 2 , where g is the foil acceleration, t is the time, and α σ is constant. The number of bubbles evolves as N(t)∝(ωt√(g)+C) -4 and the average size evolves as (t)∝ω 2 gt 2 , where C is a constant and ω=0.83±0.1 is the measured scaled bubble-merging rate

  10. Rayleigh-Taylor instabilities in indirect laser drive with rugby-shaped hohlraums

    International Nuclear Information System (INIS)

    Casner, A.; Galmiche, D.; Huser, G.; Jadaud, J.P.; Richard, A.; Liberatore, S.; Vandenboomgaerde, M.

    2009-01-01

    The mastering of the development of hydrodynamic instabilities like Rayleigh-Taylor instabilities is an important milestone on the way to perform efficient laser implosions. The complexity of these instabilities implies an experimental validation of the theoretical models and their computer simulations. An experimental platform involving the Omega laser has allowed us to perform indirect drive with rugby-shaped hohlraums. The experiments have validated the growth of 2- and 3-dimensional initial defects as predicted by theory. We have shown that the 3-dimensional defect saturates for an higher amplitude than the 2-dimensional one does. The experiments have been made by using a plastic shell doped with Germanium (CH:Ge). (A.C.)

  11. Dynamic stabilization of Rayleigh-Taylor instability: Experiments with Newtonian fluids as surrogates for ablation fronts

    International Nuclear Information System (INIS)

    Rodriguez Prieto, G.; Piriz, A. R.; Lopez Cela, J. J.; Tahir, N. A.

    2013-01-01

    A previous theory on dynamic stabilization of Rayleigh-Taylor instability at interfaces between Newtonian fluids is reformulated in order to make evident the analogy of this problem with the related one on dynamic stabilization of ablation fronts in the framework of inertial confinement fusion. Explicit analytical expressions are obtained for the boundaries of the dynamically stable region which turns out to be completely analogue to the stability charts obtained for the case of ablation fronts. These results allow proposing experiments with Newtonian fluids as surrogates for studying the case of ablation fronts. Experiments with Newtonian fluids are presented which demonstrate the validity of the theoretical approach and encourage to pursue experimental research on ablation fronts to settle the feasibility of dynamic stabilization in the inertial confinement fusion scenario.

  12. Dynamic stabilization of Rayleigh-Taylor instability in an ablation front

    International Nuclear Information System (INIS)

    Piriz, A. R.; Di Lucchio, L.; Rodriguez Prieto, G.

    2011-01-01

    Dynamic stabilization of Rayleigh-Taylor instability in an ablation front is studied by considering a modulation in the acceleration that consists of sequences of Dirac deltas. This allows obtaining explicit analytical expressions for the instability growth rate as well as for the boundaries of the stability region. As a general rule, it is found that it is possible to stabilize all wave numbers above a certain minimum value k m , but the requirements in the modulation amplitude and frequency become more exigent with smaller k m . The essential role of compressibility is phenomenologically addressed in order to find the constraint it imposes on the stability region. The results for some different wave forms of the acceleration modulation are also presented.

  13. Experimental and numerical investigations of beryllium strength models using the Rayleigh-Taylor instability

    Energy Technology Data Exchange (ETDEWEB)

    Henry de Frahan, M. T. [Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA; Belof, J. L. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Cavallo, R. M. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Raevsky, V. A. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Ignatova, O. N. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Lebedev, A. [Russian Federal Nuclear Center-VNIIEF, Sarov 607188, Russia; Ancheta, D. S. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; El-dasher, B. S. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Florando, J. N. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Gallegos, G. F. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA; Johnsen, E. [Mechanical Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA; LeBlanc, M. M. [Lawrence Livermore National Laboratory Livermore, California 94551-0808, USA

    2015-06-14

    A recent collaboration between LLNL and VNIIEF has produced a set of high explosive driven Rayleigh-Taylor strength data for beryllium. Design simulations using legacy strength models from Steinberg-Lund and Preston-Tonks-Wallace (PTW) suggested an optimal design that would delineate between not just different strength models, but different parameters sets of the PTW model. Application of the models to the post-shot results, however, shows close to classical growth. We characterize the material properties of the beryllium tested in the experiments. We also discuss recent efforts to simulate the data using the legacy strength models as well as the more recent RING relaxation model developed at VNIIEF. Finally, we present shock and ramp-loading recovery experiments conducted as part of the collaboration.

  14. Designing cylindrical implosion experiments on NIF to study deceleration phase of Rayleigh-Taylor

    Science.gov (United States)

    Vazirani, N.; Kline, J. L.; Loomis, E.; Sauppe, J. P.; Palaniyappan, S.; Flippo, K.; Srinivasan, B.; Malka, E.; Bose, A.; Shvarts, D.

    2017-10-01

    The Rayleigh-Taylor (RT) hydrodynamic instability occurs when a lower density fluid pushes on a higher density fluid. This occurs in inertial confinement fusion (ICF) implosions at each of the capsule interfaces during the initial acceleration and the deceleration as it stagnates. The RT instabilities mix capsule material into the fusion fuel degrading the Deuterium-Tritium reactivity and ultimately play a key role in limiting target performance. While significant effort has focused on understanding RT at the outer capsule surface, little work has gone into understanding the inner surface RT instability growth during the deceleration phase. Direct measurements of the RT instability are difficult to make at high convergence in a spherical implosion. Here we present the design of a cylindrical implosion system for the National Ignition Facility for studying deceleration phase RT. We will discuss the experimental design, the estimated instability growth, and our outstanding concerns.

  15. Finite-thickness effects on the Rayleigh-Taylor instability in accelerated elastic solids

    Science.gov (United States)

    Piriz, S. A.; Piriz, A. R.; Tahir, N. A.

    2017-05-01

    A physical model has been developed for the linear Rayleigh-Taylor instability of a finite-thickness elastic slab laying on top of a semi-infinite ideal fluid. The model includes the nonideal effects of elasticity as boundary conditions at the top and bottom interfaces of the slab and also takes into account the finite transit time of the elastic waves across the slab thickness. For Atwood number AT=1 , the asymptotic growth rate is found to be in excellent agreement with the exact solution [Plohr and Sharp, Z. Angew. Math. Mech. 49, 786 (1998), 10.1007/s000330050121], and a physical explanation is given for the reduction of the stabilizing effectiveness of the elasticity for the thinner slabs. The feedthrough factor is also calculated.

  16. Experiments and simulations on the incompressible, Rayleigh-Taylor instability with small wavelength initial perturbations

    Science.gov (United States)

    Roberts, Michael Scott

    The Rayleigh-Taylor instability is a buoyancy driven instability that takes place in a stratified fluid system with a constant acceleration directed from the heavy fluid into the light fluid. In this study, both experimental data and numerical simulations are presented. Experiments are performed primarily using a lithium-tungstate aqueous solution as the heavy liquid, but sometimes a calcium nitrate aqueous solution is used for comparison purposes. Experimental data is obtained for both miscible and immiscible fluid combinations. For the miscible experiments the light liquid is either ethanol or isopropanol, and for the immiscible experiments either silicone oil or trans-anethole is used. The resulting Atwood number is either 0.5 when the lithium-tungstate solution is used or 0.2 when the calcium nitrate solution is used. These fluid combinations are either forced or left unforced. The forced experiments have an initial perturbation imposed by vertically oscillating the liquid containing tank to produce Faraday waves at the interface. The unforced experiments rely on random interfacial fluctuations, due to background noise, to seed the instability. The liquid combination is partially enclosed in a test section that is accelerated downward along a vertical rail system causing the Rayleigh-Taylor instability. Accelerations of approximately 1g (with a weight and pulley system) or 10g (with a linear induction motor system) are experienced by the liquids. The tank is backlit and digitally recorded with high speed video cameras. These experiments are then simulated with the incompressible, Navier-Stokes code Miranda. The main focus of this study is the growth parameter (α) of the mixing region produced by the instability after it has become apparently self-similar and turbulent. The measured growth parameters are compared to determine the effects of miscibility and initial perturbations (of the small wavelength, finite bandwidth type used here). It is found that while

  17. Data driven modeling of the low-Atwood single-mode Rayleigh-Taylor instability

    Science.gov (United States)

    Hutchinson, Maxwell

    The Rayleigh-Taylor instability is one of the most common and well studied phenomena in fluid dynamics. Despite research dating to the late 19th century, the non-linear dynamics of the interfacial instability are still not fully understood, particularly in the case when the two fluids have nearly the same density. It was recently demonstrated in this, the low-Atwood regime, that the idealized single-mode problem departs from established potential flow models in the form of a re-acceleration beyond the predicted terminal interface velocity. This thesis is an attempt to model that re-acceleration and, more broadly, the late time dynamics of the single-mode low-Atwood Rayleigh-Taylor instability. The approach taken here is based on buoyancy-drag models, which express a force balance between buoyancy and parasitic drag. The dynamical buoyancy-drag model is supplemented with a mixing model that dilutes the buoyant force over time. These models are written deliberately generally, with 8 unique coefficients. Three of these coefficients are solved for by equating the early time behavior with that of well established linear theories. The remaining 5 coefficients are estimated by relating them to drag coefficients, friction factors, and geometric ratios in the interface shape. To evaluate the model and compute the 5 unknown coefficients more precisely, a set of direct numerical simulations are performed over the relevant parameter space. These simulations are first validated against experimental data. Then they are shown to converge and their resolutions are chosen such as to minimize computational cost given the accuracy scale of the model. The 5 coefficients are fit to the resulting data set, and the model achieves better than 2% error in the bubble height and 4% error in the volume of mixed fluid. Three coefficients are nominally independent of the parameterization of the problem, while two are shown to vary with the Rayleigh number and the diffusivity.

  18. Study of the Rayleigh-Taylor instability at the ablation front

    International Nuclear Information System (INIS)

    Salvatore, Patricia

    2000-01-01

    Inertial confinement fusion in indirect drive consists in irradiating with ultra powerful laser beams the internal wall of a heating cavity which contains a capsule enclosing the thermonuclear fuel. During laser-matter interaction, laser light is converted into x-rays onto the hohlraum walls. The x-rays capsule heating produces a matter expansion, this one induces a pressure accelerating the capsule wall which implodes and compresses the fuel. The limit between the expanded plasma and the accelerated one is named ablation front. A light fluid (the ablated plasma) accelerating a heavy one (the shell) seeds Rayleigh-Taylor instability. To perform experiments, we used the Phebus facility at Limeil-Valenton CEA (the most powerful laser in Europe). After frequency conversion, each laser beam can deliver onto a target an energy up to 3 kJ at 0.35μm wavelength. In the United States of America and in France, more powerful laser facilities are planned to deliver an energy about 1 MJ: the National Ignition Facility (Lawrence Livermore National Laboratory, California) and the Laser MegaJoule (CEA, Bordeaux). Hydrodynamic instabilities take an important part in the definition of these facilities. Two main experiments were carried out on the Phebus laser. We studied the Rayleigh-Taylor instability at the ablation front with a modulated CHBr plane target stuck on the gold hohlraum wall. During the september-october 1996 experiment, a x-ray device was used. We observed the temporal evolution of the target modulations by x-ray imaging cinematography which recorded face-on radiographs. The second experiment was performed with collaboration of the Imperial College of London. Two high spatial resolution devices (less than 5 μm) were used in order to study short wavelengths modulations. The first diagnostic recorded side-on observations of target acceleration, the second one was used to measure the instability growth with face-on radiography. We studied this growth in a modulation

  19. First observation of density profile in directly laser-driven polystyrene targets for ablative Rayleigh-Taylor instability research

    International Nuclear Information System (INIS)

    Fujioka, Shinsuke; Shiraga, Hiroyuki; Nishikino, Masaharu; Shigemori, Keisuke; Sunahara, Atsushi; Nakai, Mitsuo; Azechi, Hiroshi; Nishihara, Katsunobu; Yamanaka, Tatsuhiko

    2003-01-01

    The temporal evolution of the density profile of a directly laser-driven polystyrene target was observed for the first time using an x-ray penumbral imaging technique coupled with side-on x-ray backlighting at the GEKKO XII [C. Yamanaka et al., IEEE J. Quantum Electron. QE-17, 1639 (1981)]-High Intensity Plasma Experimental Research laser facility (I L =0.7x10 14 W/cm 2 , λ L =0.35 μm). This density measurement makes it possible to experimentally confirm all physical parameters [γ(k),k,g,m,ρ a ,L m ] appearing in the modified Takabe formula for the growth rate of the ablative Rayleigh-Taylor instability. The measured density profiles were well reproduced by a one-dimensional hydrodynamic simulation code. The density measurement contributes toward fully understanding the ablative Rayleigh-Taylor instability

  20. Power Laws and Similarity of Rayleigh-Taylor and Richtmyer-Meshkov Mixing Fronts at All Density Ratios

    International Nuclear Information System (INIS)

    Alon, U.; Hecht, J.; Ofer, D.; Shvarts, D.

    1995-01-01

    The nonlinear evolution of large structure in Rayleigh-Taylor and Richtmyer-Meshkov bubble and spike fronts is studied numerically and explained theoretically on the basis of single-mode and two-bubble interaction physics at Atwood numbers (A). Multimode Rayleigh-Taylor bubble (spike) fronts are found as h B =α B Agt 2 [h s =α s (A)gt 2 ] with α B =0.05, while Richtmyer-Meshkov bubble (spike) fronts are found as h B =a B t θ B (h s =a s t θ s (A) ) with θ B =0.4 at all A's. The dependence of these scaling laws and parameters on A and on initial conditions is explained

  1. On the ""early-time"" evolution of variables relevant to turbulence models for Rayleigh-Taylor instability

    Energy Technology Data Exchange (ETDEWEB)

    Rollin, Bertrand [Los Alamos National Laboratory; Andrews, Malcolm J [Los Alamos National Laboratory

    2010-01-01

    We present our progress toward setting initial conditions in variable density turbulence models. In particular, we concentrate our efforts on the BHR turbulence model for turbulent Rayleigh-Taylor instability. Our approach is to predict profiles of relevant parameters before the fully turbulent regime and use them as initial conditions for the turbulence model. We use an idealized model of the mixing between two interpenetrating fluids to define the initial profiles for the turbulence model parameters. Velocities and volume fractions used in the idealized mixing model are obtained respectively from a set of ordinary differential equations modeling the growth of the Rayleigh-Taylor instability and from an idealization of the density profile in the mixing layer. A comparison between predicted initial profiles for the turbulence model parameters and initial profiles of the parameters obtained from low Atwood number three dimensional simulations show reasonable agreement.

  2. On the ""early-time"" evolution of variables relevant to turbulence models for the Rayleigh-Taylor instability

    Energy Technology Data Exchange (ETDEWEB)

    Rollin, Bertrand [Los Alamos National Laboratory; Andrews, Malcolm J [Los Alamos National Laboratory

    2010-01-01

    We present our progress toward setting initial conditions in variable density turbulence models. In particular, we concentrate our efforts on the BHR turbulence model for turbulent Rayleigh-Taylor instability. Our approach is to predict profiles of relevant variables before fully turbulent regime and use them as initial conditions for the turbulence model. We use an idealized model of mixing between two interpenetrating fluids to define the initial profiles for the turbulence model variables. Velocities and volume fractions used in the idealized mixing model are obtained respectively from a set of ordinary differential equations modeling the growth of the Rayleigh-Taylor instability and from an idealization of the density profile in the mixing layer. A comparison between predicted profiles for the turbulence model variables and profiles of the variables obtained from low Atwood number three dimensional simulations show reasonable agreement.

  3. RAYLEIGH-TAYLOR STRENGTH EXPERIMENTS OF THE PRESSURE-INDUCED alpha->epsilon->alpha' PHASE TRANSITION IN IRON

    Energy Technology Data Exchange (ETDEWEB)

    Belof, J L; Cavallo, R M; Olson, R T; King, R S; Gray, G T; Holtkamp, D B; Chen, S R; Rudd, R E; Barton, N R; Arsenlis, A; Remington, B A; Park, H; Prisbrey, S T; Vitello, P A; Bazan, G; Mikaelian, K O; Comley, A J; Maddox, B R; May, M J

    2011-08-10

    We present here the first dynamic Rayleigh-Taylor (RT) strength measurement of a material undergoing solid-solid phase transition. Iron is quasi-isentropically driven across the pressure-induced bcc ({alpha}-Fe) {yields} hcp ({var_epsilon}-Fe) phase transition and the dynamic strength of the {alpha}, {var_epsilon} and reverted {alpha}{prime} phases have been determined via proton radiography of the resulting Rayleigh-Taylor unstable interface between the iron target and high-explosive products. Simultaneous velocimetry measurements of the iron free surface yield the phase transition dynamics and, in conjunction with detailed hydrodynamic simulations, allow for determination of the strength of the distinct phases of iron. Forward analysis of the experiment via hydrodynamic simulations reveals significant strength enhancement of the dynamically-generated {var_epsilon}-Fe and reverted {alpha}{prime}-Fe, comparable in magnitude to the strength of austenitic stainless steels.

  4. Evidence for a bubble-competition regime in indirectly driven ablative Rayleigh-Taylor instability experiments on the NIF.

    Science.gov (United States)

    Martinez, D A; Smalyuk, V A; Kane, J O; Casner, A; Liberatore, S; Masse, L P

    2015-05-29

    We investigate on the National Ignition Facility the ablative Rayleigh-Taylor instability in the transition from weakly nonlinear to highly nonlinear regimes. A planar plastic package with preimposed two-dimensional broadband modulations is accelerated for up to 12 ns by the x-ray drive of a gas-filled Au radiation cavity with a radiative temperature plateau at 175 eV. This extended tailored drive allows a distance traveled in excess of 1 mm for a 130  μm thick foil. Measurements of the modulation optical density performed by x-ray radiography show that a bubble-merger regime for the Rayleigh-Taylor instability at an ablation front is achieved for the first time in indirect drive. The mutimode modulation amplitudes are in the nonlinear regime, grow beyond the Haan multimode saturation level, evolve toward the longer wavelengths, and show insensitivity to the initial conditions.

  5. Using the self-learning intellectual models for predicting the development of the Rayleigh-Taylor turbulent mixing

    International Nuclear Information System (INIS)

    Nuzhnyj, A.S.; Rozanov, V.B.; Stepanov, R.V.; Shumskij, S.A.

    2005-01-01

    Stability of target compression in the laser thermonuclear synthesis is discussed. The process is determined by developing the Rayleigh-Taylor instability (RNI). A program unit for description of the RNI evolution by its initial distributions is developed. The results of statistical analysis of the RT mixing calculations are given. The analysis is carried out by means of learning base system and is substantiated on the generalization of great number of data, fulfilled by means of the neural network methods [ru

  6. Evidence for a Rayleigh-Taylor type instability and upwelling of depleted density regions during equatorial spread F

    International Nuclear Information System (INIS)

    Kelley, M.C.; Haerendel, G.; Kappler, H.; Valenzuela, A.; Balsley, B.B.; Carter, D.A.; Ecklund, W.L.; Carlson, C.W.; Hausler, B.; Torbert, R.

    1976-01-01

    Recent rocket probe, barium cloud and radar measurements conducted during equatorial spread F conditions are interpreted in terms of a Rayleigh-Taylor gravitational instability operating on the bottomside of the F peak. The persistent theoretical problems associated with strong radar echoes typically observed in patch-like structures at high altitudes are explained in terms of regions of depleted plasma density which bouyantly rise against the gravitational field

  7. A heuristic model for the nonlinear Rayleigh--Taylor instability in fast Z pinches

    International Nuclear Information System (INIS)

    Hussey, T.W.; Roderick, N.F.; Shumlak, U.; Spielman, R.B.; Deeney, C.

    1995-01-01

    A simple, heuristic model for the early nonlinear phase of the Rayleigh--Taylor instability (RTI) in thin-cylindrical-shell Z-pinch implosions has been developed. This model is based on the fact that, as the field--plasma interface is deformed, there is a component of the applied force that acts to move mass from the low mass per unit area bubble region into the higher mass per unit area spike region. The resulting reduced mass per unit area of the bubble causes it to be preferentially accelerated ahead of the spike. The pinch begins to radiate as the bubble mass first reaches the axis, and it continues to radiate while the mass that is entrained within the spikes and within unperturbed parts of the shell also arrives on axis. This model relates the time at which the bubble arrives on axis to an initial wavelength and amplitude of a single mode of the RTI. Then, by comparing this to the time at which the unperturbed mass reaches the axis, one estimates pinch thermalization time, a quantity that is determined experimentally. Experimental data, together with analytic models, have been used to choose appropriate initial wavelength and amplitude both for foils and for certain gas puff implosions. By noting that thermalization time is a weak function of these parameters, it is argued that one may use the same values for an extrapolative study of qualitatively similar implosions

  8. Stabilization of the Rayleigh-Taylor instability by convection in an ablatively accelerated laser plasma

    International Nuclear Information System (INIS)

    Bul'ko, A.B.; Liberman, M.A.

    1992-01-01

    The authors use the WKB-approximation to treat the problem of the stabilization by an inhomogeneous convective current of the Rayleigh-Taylor instability developing in the ablation zone when the plasma of laser targets is accelerated by ablation. The problem of the eigenvalues - the instability growth rates - is reduced to the solution of an algebraic equation with coefficients which depend on the structure of the unperturbed profiles of the hydrodynamic variables. They show for the practically important case of subsonic flow of an incompressible plasma that the instability growth rate vanishes for k = k o = max[2(g|∇lnρ|) 1/2 /v]. The condition for the self-consistency of the model is that the local Froude number be small in the region where the instability develops; however, comparison with numerical calculations shows that the model is also applicable in the case of rather steep density gradients when the Froude number is of order unity. 32 refs., 2 figs

  9. Progress in understanding turbulent mixing induced by Rayleigh-Taylor and Richtmyer-Meshkov instabilities

    International Nuclear Information System (INIS)

    Zhou Ye; Remington, B.A.; Robey, H.F.; Cook, A.W.; Glendinning, S.G.; Dimits, A.; Buckingham, A.C.; Zimmerman, G.B.; Burke, E.W.; Peyser, T.A.; Cabot, W.; Eliason, D.

    2003-01-01

    Turbulent hydrodynamic mixing induced by the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities occurs in settings as varied as exploding stars (supernovae), inertial confinement fusion (ICF) capsule implosions, and macroscopic flows in fluid dynamics facilities such as shock tubes. Turbulence theory and modeling have been applied to RT and RM induced flows and developed into a quantitative description of turbulence from the onset to the asymptotic end-state. The treatment, based on a combined approach of theory, direct numerical simulation (DNS), and experimental data analysis, has broad generality. Three areas of progress will be reported. First, a robust, easy to apply criteria will be reported for the mixing transition in a time-dependent flow. This allows an assessment of whether flows, be they from supernova explosions or ICF experiments, should be mixed down to the molecular scale or not. Second, through DNS, the structure, scaling, and spectral evolution of the RT instability induced flow will be inspected. Finally, using these new physical insights, a two-scale, dynamic mix model has been developed that can be applied to simulations of ICF experiments and astrophysics situations alike

  10. Rayleigh-Taylor instability and resulting failure modes of ablatively imploded inertial fusion targets

    International Nuclear Information System (INIS)

    Montierth, L.; Morse, R.

    1984-01-01

    This chapter discusses small amplitude growth of the outside surface instability and modes of failure resulting from nonlinear development of the inside surface instability. It is demonstrated that pellets with initial pellet aspect ratio, A /SUB p/ >5 may have difficulty with Rayleigh-Taylor instability and that shells with A /SUB p/ greater than or equal to10 will probably demand stringent smoothness specification in order not to experience failure in the final implosion. The linear amplification of the outside surface instability can easily exceed 10 3 for A /SUB p/ and resulting A values in the range of programmatic interest. Amplifications of this order, starting from attainable surface finishes, can then penetrate to the inside shell surface, producing perturbations there which approach the nonlinear development amplitude and at the start of the final deceleration. It is shown that such inside surface perturbations can be amplified to large amplitude by the inside instability and cause failure through reduction of the maximum fuel temperature achieved. Insight into the scaling of failure mechanisms is offered

  11. Spanwise homogeneous buoyancy-drag model for Rayleigh-Taylor mixing and experimental evaluation

    International Nuclear Information System (INIS)

    Dimonte, Guy

    2000-01-01

    A buoyancy-drag model for Rayleigh-Taylor (RT) mixing is developed on the premise that the bubble and spike regions behave as distinct and spanwise homogeneous fluids. Then, mass conservation is applied accross the mixing zone to obtain their average mixture densities dynamically. These are used to explicitly calculate the inertia and buoyancy terms in the evolutionary equation. The only unknown parameter in the model is the Newtonian drag constant C∼2.5±0.6, which is determined from turbulent RT experiments over various Atwood numbers A and acceleration histories g(t). The bubble (i=2) and spike (i=1) amplitudes are found to obey the familiar h i =α i Agt 2 for a constant g and h i ∼t θ i for an impulsive g. For bubbles, both α 2 and θ 2 are insensitive to A. For the spikes, both α 1 and θ 1 increase as a power law with the density ratio. However, θ 1 is not universal because it depends on the initial value of h 1 /h 2 . (c) 2000 American Institute of Physics

  12. Suppression of the Rayleigh Taylor instability and its implication for the impact ignition

    Science.gov (United States)

    Azechi, H.; Shiraga, H.; Nakai, M.; Shigemori, K.; Fujioka, S.; Sakaiya, T.; Tamari, Y.; Ohtani, K.; Murakami, M.; Sunahara, A.; Nagatomo, H.; Nishihara, K.; Miyanaga, N.; Izawa, Y.

    2004-12-01

    The Rayleigh Taylor (RT) instability with material ablation through an unstable interface is the key physics that determines the success or failure of inertial fusion energy (IFE) generation, as the RT instability potentially quenches ignition and burn by disintegrating the IFE target. We present two suppression schemes of the RT growth without significant degradation of the target density. The first scheme is to generate a double ablation structure in high-Z doped plastic targets. In addition to the electron ablation surface, a new ablation surface is created by x-ray radiation from the high-Z ions. Contrary to the previous thought, the electron ablation surface is almost completely stabilized by extremely high flow velocity. On the other hand, the RT instability on the radiative ablation surface is significantly moderated. The second is to enhance the nonlocal nature of the electron heat transport by illuminating the target with long wavelength laser light, whereas the high ablation pressure is generated by irradiating with short wavelength laser light. The significant suppression of the RT instability may increase the possibility of impact ignition which uses a high-velocity fuel colliding with a preformed main fuel.

  13. Multiscale character of the nonlinear coherent dynamics in the Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Abarzhi, S.I.; Nishihara, K.; Rosner, R.

    2006-01-01

    We report nonlinear solutions for a system of conservation laws describing the dynamics of the large-scale coherent structure of bubbles and spikes in the Rayleigh-Taylor instability (RTI) for fluids with a finite density ratio. Three-dimensional flows are considered with general type of symmetry in the plane normal to the direction of gravity. The nonlocal properties of the interface evolution are accounted for on the basis of group theory. It is shown that isotropic coherent structures are stable. For anisotropic structures, secondary instabilities develop with the growth rate determined by the density ratio. For stable structures, the curvature and velocity of the nonlinear bubble have nontrivial dependencies on the density ratio, yet their mutual dependence on one another has an invariant form independent of the density ratio. The process of bubble merge is not considered. Based on the obtained results we argue that the large-scale coherent dynamics in RTI has a multiscale character and is governed by two length scales: the period of the coherent structure and the bubble (spike) position

  14. Bubble velocity in the nonlinear Rayleigh-Taylor instability at a deflagration front

    International Nuclear Information System (INIS)

    Modestov, Mikhail; Bychkov, Vitaly; Betti, Riccardo; Eriksson, Lars-Erik

    2008-01-01

    The Rayleigh-Taylor instability at a deflagration front is studied systematically using extensive direct numerical simulations. It is shown that, for a sufficiently large gravitational field, the effects of bubble rising dominate the deflagration dynamics. It is demonstrated both analytically and numerically that the deflagration speed is described asymptotically by the Layzer theory in the limit of large acceleration. In the opposite limit of small and zero gravitational field, intrinsic properties of the deflagration front become important. In that case, the deflagration speed is determined by the velocity of a planar front and by the Darrieus-Landau instability. Because of these effects, the deflagration speed is larger than predicted by the Layzer theory. An analytical formula for the deflagration speed is suggested, which matches two asymptotic limits of large and small acceleration. The formula is in good agreement with the numerical data in a wide range of Froude numbers. The present results are also in agreement with previous numerical simulations on this problem

  15. 3-D simulations to investigate initial condition effects on the growth of Rayleigh-Taylor mixing

    Energy Technology Data Exchange (ETDEWEB)

    Andrews, Malcolm J [Los Alamos National Laboratory

    2008-01-01

    The effect of initial conditions on the growth rate of turbulent Rayleigh-Taylor (RT) mixing has been studied using carefully formulated numerical simulations. An integrated large-eddy simulation (ILES) that uses a finite-volume technique was employed to solve the three-dimensional incompressible Euler equations with numerical dissipation. The initial conditions were chosen to test the dependence of the RT growth parameters ({alpha}{sub b}, {alpha}{sub s}) on variations in (a) the spectral bandwidth, (b) the spectral shape, and (c) discrete banded spectra. Our findings support the notion that the overall growth of the RT mixing is strongly dependent on initial conditions. Variation in spectral shapes and bandwidths are found to have a complex effect of the late time development of the RT mixing layer, and raise the question of whether we can design RT transition and turbulence based on our choice of initial conditions. In addition, our results provide a useful database for the initialization and development of closures describing RT transition and turbulence.

  16. Single-mode Rayleigh-Taylor growth-rate measurements with the OMEGA laser system

    International Nuclear Information System (INIS)

    Knauer, J.P.; Verdon, C.P.; Meyerhofer, D.D.; Boehly, T.R.; Bradley, D.K.; Smalyuk, V.A.; Ofer, D.; McKenty, P.W.; Glendinning, S.G.; Kalantar, D.H.; Watt, R.G.; Gobby, P.L.; Willi, O.; Taylor, R.J.

    1997-01-01

    The results from a series of single-mode Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five to six 351-nm laser beams overlapped with total intensities up to 2.5x10 14 W/cm 2 . Experiments were performed with both 3-ns ramp and 3-ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%endash 7% over a 600-μm-diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using through-foil radiography and was detected with an x-ray framing camera for CH targets with and without a foam buffer. The growth of both 31-μm and 60-μm wavelength perturbations was found to be in good agreement with ORCHID simulations when the experimental details, including noise, were included. The addition of a 30-mg/cc, 100-μm-thick polystyrene foam buffer layer resulted in reduced growth of the 31-μm perturbation and essentially unchanged growth for the 60-μm case when compared to targets without foam. copyright 1997 American Institute of Physics

  17. Interface width effect on the classical Rayleigh-Taylor instability in the weakly nonlinear regime

    International Nuclear Information System (INIS)

    Wang, L. F.; Ye, W. H.; Li, Y. J.

    2010-01-01

    In this paper, the interface width effects (i.e., the density gradient effects or the density transition layer effects) on the Rayleigh-Taylor instability (RTI) in the weakly nonlinear (WN) regime are investigated by numerical simulation (NS). It is found that the interface width effects dramatically influence the linear growth rate in the linear growth regime and the mode coupling process in the WN growth regime. First, the interface width effects decrease the linear growth rate of the RTI, particularly for the short perturbation wavelengths. Second, the interface width effects suppress (reduce) the third-order feedback to the fundamental mode, which induces the nonlinear saturation amplitude (NSA) to exceed the classical prediction, 0.1λ. The wider the density transition layer is, the larger the NSA is. The NSA in our NS can reach a half of its perturbation wavelength. Finally, the interface width effects suppress the generation and the growth of the second and the third harmonics. The ability to suppress the harmonics' growth increases with the interface width but decreases with the perturbation wavelength. On the whole, in the WN regime, the interface width effects stabilize the RTI, except for an enhancement of the NSA, which is expected to improve the understanding of the formation mechanism for the astrophysical jets, and for the jetlike long spikes in the high energy density physics.

  18. Modeling and simulations of radiative blast wave driven Rayleigh-Taylor instability experiments

    Science.gov (United States)

    Shimony, Assaf; Huntington, Channing M.; Trantham, Matthew; Malamud, Guy; Elbaz, Yonatan; Kuranz, Carolyn C.; Drake, R. Paul; Shvarts, Dov

    2017-10-01

    Recent experiments at the National Ignition Facility measured the growth of Rayleigh-Taylor RT instabilities driven by radiative blast waves, relevant to astrophysics and other HEDP systems. We constructed a new Buoyancy-Drag (BD) model, which accounts for the ablation effect on both bubble and spike. This ablation effect is accounted for by using the potential flow model ]Oron et al PoP 1998], adding another term to the classical BD formalism: βDuA / u , where β the Takabe constant, D the drag term, uA the ablation velocity and uthe instability growth velocity. The model results are compared with the results of experiments and 2D simulations using the CRASH code, with nominal radiation or reduced foam opacity (by a factor of 1000). The ablation constant of the model, βb / s, for the bubble and for the spike fronts, are calibrated using the results of the radiative shock experiments. This work is funded by the Lawrence Livermore National Laboratory under subcontract B614207, and was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  19. Planar Rayleigh-Taylor and Feed-through experiments with CH(Ge) on OMEGA

    International Nuclear Information System (INIS)

    Casner, A.; Huser, G.; Jadaud, J.P.; Liberatore, S.; Galmiche, D.; Vandenboomgaerde, M.

    2006-01-01

    Germanium-doped CH (CHGe) is one nominal ablator for the laser Megajoule (LMJ) target design. In order to investigate its properties we performed indirect drive planar Rayleigh-Taylor experiments on the OMEGA laser facility. An innovative hohlraum with an internal 'rugby-ball' shape has been experimentally characterized for the first time. On each shot foil motion and modulations growth were simultaneously measured by side-on and face-on radiography, while drive was assessed by measuring radiation escaping through the hohlraum laser-entrance-hole. Modulations growth and foil motion are fully consistent with each other, and also with hydro-code simulations accounting for the effective acceleration of the sample. This complete set of data allows a more stringent comparison between the hydro-code simulations and the experimental results. We compare CHGe perturbations growth with those acquired on CHBr in the same experimental configuration. These preliminary results are the first step toward a test-bed validation of CH(Ge) as an ablator on OMEGA and further on the laser integration line (LIL) at LMJ

  20. An Investigation of the Influence of Initial Conditions on Rayleigh-Taylor Mixing

    Energy Technology Data Exchange (ETDEWEB)

    Mueschke, Nicholas J. [Texas A & M Univ., College Station, TX (United States)

    2004-12-01

    Experiments and direct numerical simulations (DNS) have been performed to examine the effects of initial conditions on the dynamics of a Rayleigh-Taylor unstable mixing layer. Experiments were performed on a water channel facility to measure the interfacial and velocity perturbations initially present at the two-fluid interface in a small Atwood number mixing layer. The experimental measurements have been parameterized for use in numerical simulations of the experiment. Two- and three-dimensional DNS of the experiment have been performed using the parameterized initial conditions. It is shown that simulations implemented with initial velocity and density perturbations, rather than density perturbations alone, are required to match experimentally-measured statistics and spectra. Data acquired from both the experiment and numerical simulations are used to examine the role of initial conditions on the evolution of integral-scale, turbulence, and mixing statistics. Early-time turbulence and mixing statistics are shown to be strongly-dependent upon the early-time transition of the initial perturbation from a weakly-nonlinear to a strongly-nonlinear flow.

  1. Rayleigh-Taylor convection of immiscible fluids in three-dimensional porous media

    Science.gov (United States)

    Giurgiu, Vlad; de Paoli, Marco; Zonta, Francesco; Soldati, Alfredo

    2017-11-01

    The Rayleigh-Taylor instability of two immiscible fluids is studied by means of a Phase-Field Method (PFM). With this description, the fluid-fluid interface is modeled as a thin transition layer where all the thermophysical properties vary rapidly but without discontinuities. This is achieved by introducing a phase indicator that is uniform in the bulk phases and varies across the thin separation interface between the two phases. This provides the accurate description of the interfacial dynamics, which is required to improve the current physical modeling of the transfer mechanisms between the two fluids in the present situation (not yet available). The fluid velocity is determined by the Darcy law, where the surface tension effects are also accounted for, whereas the concentration field is determined by the Cahn-Hilliard equation. Current results obtained in the 3D configuration are also compared with results obtained in the 2D case to highlight the possible modifications of the flow topology coming from the coupled interaction between surface tension and gravity effects in a 3D environment.

  2. Algorithm and exploratory study of the Hall MHD Rayleigh-Taylor instability.

    Energy Technology Data Exchange (ETDEWEB)

    Gardiner, Thomas Anthony

    2010-09-01

    This report is concerned with the influence of the Hall term on the nonlinear evolution of the Rayleigh-Taylor (RT) instability. This begins with a review of the magnetohydrodynamic (MHD) equations including the Hall term and the wave modes which are present in the system on time scales short enough that the plasma can be approximated as being stationary. In this limit one obtains what are known as the electron MHD (EMHD) equations which support two characteristic wave modes known as the whistler and Hall drift modes. Each of these modes is considered in some detail in order to draw attention to their key features. This analysis also serves to provide a background for testing the numerical algorithms used in this work. The numerical methods are briefly described and the EMHD solver is then tested for the evolution of whistler and Hall drift modes. These methods are then applied to study the nonlinear evolution of the MHD RT instability with and without the Hall term for two different configurations. The influence of the Hall term on the mixing and bubble growth rate are analyzed.

  3. Drive development for an 10 Mbar Rayleigh-Taylor strength experiment on the National Ignition Facility

    Science.gov (United States)

    Prisbrey, Shon; Park, Hye-Sook; Huntington, Channing; McNaney, James; Smith, Raym; Wehrenberg, Christopher; Swift, Damian; Panas, Cynthia; Lord, Dawn; Arsenlis, Athanasios

    2017-10-01

    Strength can be inferred by the amount a Rayleigh-Taylor surface deviates from classical growth when subjected to acceleration. If the acceleration is great enough, even materials highly resistant to deformation will flow. We use the National Ignition Facility (NIF) to create an acceleration profile that will cause sample metals, such as Mo or Cu, to reach peak pressures of 10 Mbar without inducing shock melt. To create such a profile we shock release a stepped density reservoir across a large gap with the stagnation of the reservoir on the far side of the gap resulting in the desired pressure drive history. Low density steps (foams) are a necessary part of this design and have been studied in the last several years on the Omega and NIF facilities. We will present computational and experimental progress that has been made on the 10 Mbar drive designs - including recent drive shots carried out at the NIF. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344. LLNL-ABS-734781.

  4. Adjoint-based approach to Enhancing Mixing in Rayleigh-Taylor Turbulence

    Science.gov (United States)

    Kord, Ali; Capecelatro, Jesse

    2016-11-01

    A recently developed adjoint method for multi-component compressible flow is used to measure sensitivity of the mixing rate to initial perturbations in Rayleigh-Taylor (RT) turbulence. Direct numerical simulations (DNS) of RT instabilities are performed at moderate Reynolds numbers. The DNS are used to provide an initial prediction, and the corresponding space-time discrete-exact adjoint provides a sensitivity gradient for a specific quantity of interest (QoI). In this work, a QoI is defined based on the time-integrated scalar field to quantify the mixing rate. Therefore, the adjoint solution is used to measure sensitivity of this QoI to a set of initial perturbations, and inform a gradient-based line search to optimize mixing. We first demonstrate the adjoint approach in the linear regime and compare the optimized initial conditions to the expected values from linear stability analysis. The adjoint method is then used in the high Reynolds number limit where theory is no longer valid. Finally, chaos is known to contaminate the accuracy of the adjoint gradient in turbulent flows when integrated over long time horizons. We assess the influence of chaos on the accuracy of the adjoint gradient to guide the work of future studies on adjoint-based sensitivity of turbulent mixing. PhD Student, Department of Mechanical Engineering, University of Michigan, Ann Arbor, MI.

  5. What controls Rayleigh-Taylor instability growth rate and the formation of bubbles?

    Science.gov (United States)

    Yizengaw, E.; Moldwin, M.; Zesta, E.; Damtie, B.; Rabiu, B.; Valladares, C. E.; Stoneback, R.

    2014-12-01

    According to the Rayleigh-Taylor instability (RTI) growth rate mathematical expression, the vertical drift is supposed to be the primary component that controls the RTI growth rate. However, in the African sector that does not seem to be the case. In this paper we present independent ground- and space-based observations that consistently show weaker vertical drift (both dayside and evening sector) in the African sector compared with the American sector. On the other hand, observations from both satellite and recently deployed ground-based instruments have shown that the African sector is home to stronger and year-round ionospheric bubbles/irregularities and scintillations compared to the American and Asian sectors. The question is if the drift is weaker in the African sector, what causes these strong bubbles that have been observed in the African sector almost throughout the night and during all seasons? Are there other mechanisms that initiate RTI growth other than vertical drift? Would it be the neutral winds that cause the long lasting bubbles in Africa? If it is the neutral wind, why are the winds unique in terms of orientation and magnitude in the African sector compared to other longitudinal sectors?

  6. Investigation of the Rayleigh-Taylor and Richtmyer-Meshkov instabilities

    International Nuclear Information System (INIS)

    Riccardo Bonazza

    2006-01-01

    The present research program is centered on the experimental and numerical study of two instabilities that develop at the interface between two different fluids when the interface experiences an impulsive or a constant acceleration. The instabilities, called the Richtmyer-Meshkov and Rayleigh-Taylor instability, respectively (RMI and RTI), adversely affect target implosion in experiments aimed at the achievement of nuclear fusion by inertial confinement by causing the nuclear fuel contained in a target and the ablated shell material to mix, leading to contamination of the fuel, yield reduction or no ignition at all. Specifically, our work is articulated in three main directions: study of impulsively accelerated spherical gas inhomogeneities; study of impulsively accelerated 2-D interfaces; study of a liquid interface under the action of gravity. The objectives common to all three activities are to learn some physics directly from our experiments and calculations; and to develop a database at previously untested conditions to be used to calibrate and verify some of the computational tools being developed within the RTI/RMI community at the national laboratories and the ASCI centers

  7. Developpement of a numerical method for Navier-Stokes equations in anelastic approximation: application to Rayleigh-Taylor instabilities

    International Nuclear Information System (INIS)

    Hammouch, Z.

    2012-01-01

    The 'anelastic' approximation allows us to filter the acoustic waves thanks to an asymptotic development of the Navier-Stokes equations, so increasing the averaged time step, during the numerical simulation of hydrodynamic instabilities development. So, the anelastic equations for a two fluid mixture in case of Rayleigh-Taylor instability are established.The linear stability of Rayleigh-Taylor flow is studied, for the first time, for perfect fluids in the anelastic approximation. We define the Stokes problem resulting from Navier-Stokes equations without the non linear terms (a part of the buoyancy is considered); the ellipticity is demonstrated, the Eigenmodes and the invariance related to the pressure are detailed. The Uzawa's method is extended to the anelastic approximation and shows the decoupling speeds in 3D, the particular case k = 0 and the spurious modes of pressure. Passing to multi-domain allowed to establish the transmission conditions.The algorithms and the implementation in the existing program are validated by comparing the Uzawa's operator in Fortran and Mathematica languages, to an experiment with incompressible fluids and results from anelastic and compressible numerical simulations. The study of the influence of the initial stratification of both fluids on the development of the Rayleigh-Taylor instability is initiated. (author) [fr

  8. Stationary solution of the Rayleigh-Taylor instability for spatially periodic flows: questions of uniqueness, dimensionality, and universality

    International Nuclear Information System (INIS)

    Abarzhi, S.I.

    1996-01-01

    The stationary solutions of the Rayleigh-Taylor instability for spatially periodic flows with general symmetry are investigated here for the first time. The existence of a set of stationary solutions is established. The question of its dimensionality in function space is resolved on the basis of an analysis of the symmetry of the initial perturbation. The interrelationship between the dimensionality of the solution set and the symmetry of the flow is found. The dimensionality of the solution set is established for flows invariant with respect to one of five symmorphic two-dimensional groups. The nonuniversal character of the set of stationary solutions of the Rayleigh-Taylor instability is demonstrated. For flows in a tube, on the contrary, universality of the solution set, along with its independence of the symmetry of the initial perturbation, is assumed. The problem of the free boundary in the Rayleigh-Taylor instability is solved in the first two approximations, and their convergence is investigated. The dependence of the velocity and Fourier harmonics on the parameters of the problem is found. Possible symmetry violations of the flow are analyzed. Limits to previously studied cases are investigated, and their accuracy is established. Questions of the stability of the solutions obtained and the possibility of a physically correct statement of the problem are discussed

  9. Saturation and postsaturation phenomena of Rayleigh-Taylor instability with adjacent modes

    International Nuclear Information System (INIS)

    Ikegawa, Tadashi; Nishihara, Katsunobu

    2003-01-01

    A weakly nonlinear theory has been developed for the classical Rayleigh-Taylor instability with a finite bandwidth taken into account self-consistently. The theory includes up to third order nonlinearity, which results in the saturation of linear growth and determines subsequent weakly nonlinear growth. Analytical results are shown to agree fairly well with two-dimensional hydrodynamic simulations. There are generally many local peaks of a perturbation with a finite bandwidth due to the interference of modes. Since a local amplitude is determined from phases among the modes as well as the bandwidth, we have investigated an onset of the linear growth saturation and the subsequent weakly nonlinear growth for different bandwidths and phases. It is shown that the saturation of the linear growth occurs locally, i.e., each of the local maximum amplitudes (LMAs) grows exponentially until it reaches almost the same saturation amplitude. In the random phase case, the root mean square amplitude thus saturates with almost the same amplitude as the LMA, after most of the LMAs have saturated. The saturation amplitude of the LMA is found to be independent of the bandwidth and depends on the Atwood number. We derive a formula of the saturation amplitude of modes based on the results obtained, and discuss its relation with Haan's formula [Phys. Rev. A 39, 5812 (1989)]. The LMAs grow linearly in time after the saturation and their speeds are approximated by the product of the linear growth rate and the saturation amplitude. We investigate the Atwood number dependence of both the saturation amplitude and the weakly nonlinear growth

  10. Single-mode, Rayleigh-Taylor growth-rate measurements on the OMEGA laser system

    International Nuclear Information System (INIS)

    Knauer, J. P.; Betti, R.; Bradley, D. K.; Boehly, T. R.; Collins, T. J. B.; Goncharov, V. N.; McKenty, P. W.; Meyerhofer, D. D.; Smalyuk, V. A.; Verdon, C. P.

    2000-01-01

    The results from a series of single-mode, Rayleigh-Taylor (RT) instability growth experiments performed on the OMEGA laser system [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)] using planar targets are reported. Planar targets with imposed mass perturbations were accelerated using five or six 351 nm laser beams overlapped with total intensities up to 2.5x10 14 W/cm 2 . Experiments were performed with both 3 ns ramp and 3 ns flat-topped temporal pulse shapes. The use of distributed phase plates and smoothing by spectral dispersion resulted in a laser-irradiation nonuniformity of 4%-7% over a 600 μm diam region defined by the 90% intensity contour. The temporal growth of the modulation in optical depth was measured using throughfoil radiography and was detected with an x-ray framing camera for CH targets. Two-dimensional (2-D) hydrodynamic simulations (ORCHID) [R. L. McCrory and C. P. Verdon, in Inertial Confinement Fusion (Editrice Compositori, Bologna, 1989), pp. 83-124] of the growth of 20, 31, and 60 μm wavelength perturbations were in good agreement with the experimental data when the experimental details, including noise, were included. The amplitude of the simulation optical depth is in good agreement with the experimental optical depth; therefore, great care must be taken when the growth rates are compared to dispersion formulas. Since the foil's initial condition just before it is accelerated is not that of a uniformly compressed foil, the optical density measurement does not accurately reflect the amplitude of the ablation surface but is affected by the initial nonuniform density profile. (c) 2000 American Institute of Physics

  11. Experimental techniques for measuring Rayleigh-Taylor instability in inertial confinement fusion (ICF)

    Energy Technology Data Exchange (ETDEWEB)

    Smalyuk, V A

    2012-06-07

    Rayleigh-Taylor (RT) instability is one of the major concerns in inertial confinement fusion (ICF) because it amplifies target modulations in both acceleration and deceleration phases of implosion, which leads to shell disruption and performance degradation of imploding targets. This article reviews experimental results of the RT growth experiments performed on OMEGA laser system, where targets were driven directly with laser light. RT instability was studied in the linear and nonlinear regimes. The experiments were performed in acceleration phase, using planar and spherical targets, and in deceleration phase of spherical implosions, using spherical shells. Initial target modulations consisted of 2-D pre-imposed modulations, and 2-D and 3-D modulations imprinted on targets by the non-uniformities in laser drive. In planar geometry, the nonlinear regime was studied using 3-D modulations with broadband spectra near nonlinear saturation levels. In acceleration-phase, the measured modulation Fourier spectra and nonlinear growth velocities are in good agreement with those predicted by Haan's model [Haan S W 1989 Phys. Rev. A 39 5812]. In a real-space analysis, the bubble merger was quantified by a self-similar evolution of bubble size distributions [Oron D et al 2001 Phys. Plasmas 8, 2883]. The 3-D, inner-surface modulations were measured to grow throughout the deceleration phase of spherical implosions. RT growth rates are very sensitive to the drive conditions, therefore they can be used to test and validate drive physics in hydrodynamic codes used to design ICF implosions. Measured growth rates of pre-imposed 2-D target modulations below nonlinear saturation levels were used to validate non-local thermal electron transport model in laser-driven experiments.

  12. Preheating ablation effects on the Rayleigh-Taylor instability in the weakly nonlinear regime

    International Nuclear Information System (INIS)

    Wang, L. F.; Ye, W. H.; He, X. T.; Sheng, Z. M.; Don, Wai-Sun; Li, Y. J.

    2010-01-01

    The two-dimensional Rayleigh-Taylor instability (RTI) with and without thermal conduction is investigated by numerical simulation in the weakly nonlinear regime. A preheat model κ(T)=κ SH [1+f(T)] is introduced for the thermal conduction [W. H. Ye, W. Y. Zhang, and X. T. He, Phys. Rev. E 65, 057401 (2002)], where κ SH is the Spitzer-Haerm electron thermal conductivity coefficient and f(T) models the preheating tongue effect in the cold plasma ahead of the ablation front. The preheating ablation effects on the RTI are studied by comparing the RTI with and without thermal conduction with identical density profile relevant to inertial confinement fusion experiments. It is found that the ablation effects strongly influence the mode coupling process, especially with short perturbation wavelength. Overall, the ablation effects stabilize the RTI. First, the linear growth rate is reduced, especially for short perturbation wavelengths and a cutoff wavelength is observed in simulations. Second, the second harmonic generation is reduced for short perturbation wavelengths. Third, the third-order negative feedback to the fundamental mode is strengthened, which plays a stabilization role. Finally, on the contrary, the ablation effects increase the generation of the third harmonic when the perturbation wavelengths are long. Our simulation results indicate that, in the weakly nonlinear regime, the ablation effects are weakened as the perturbation wavelength is increased. Numerical results obtained are in general agreement with the recent weakly nonlinear theories as proposed in [J. Sanz, J. Ramirez, R. Ramis et al., Phys. Rev. Lett. 89, 195002 (2002); J. Garnier, P.-A. Raviart, C. Cherfils-Clerouin et al., Phys. Rev. Lett. 90, 185003 (2003)].

  13. Indirect drive ablative Rayleigh-Taylor experiments with rugby hohlraums on OMEGA

    Science.gov (United States)

    Casner, A.; Galmiche, D.; Huser, G.; Jadaud, J.-P.; Liberatore, S.; Vandenboomgaerde, M.

    2009-09-01

    Results of ablative Rayleigh-Taylor instability growth experiments performed in indirect drive on the OMEGA laser facility [T. R. Boehly, D. L. Brown, S. Craxton et al., Opt. Commun. 133, 495 (1997)] are reported. These experiments aim at benchmarking hydrocodes simulations and ablator instabilities growth in conditions relevant to ignition in the framework of the Laser MégaJoule [C. Cavailler, Plasma Phys. Controlled Fusion 47, 389 (2005)]. The modulated samples under study were made of germanium-doped plastic (CHGe), which is the nominal ablator for future ignition experiments. The incident x-ray drive was provided using rugby-shaped hohlraums [M. Vandenboomgaerde, J. Bastian, A. Casner et al., Phys. Rev. Lett. 99, 065004 (2007)] and was characterized by means of absolute time-resolved soft x-ray power measurements through a dedicated diagnostic hole, shock breakout data and one-dimensional and two-dimensional (2D) side-on radiographies. All these independent x-ray drive diagnostics lead to an actual on-foil flux that is about 50% smaller than laser-entrance-hole measurements. The experimentally inferred flux is used to simulate experimental optical depths obtained from face-on radiographies for an extensive set of initial conditions: front-side single-mode (wavelength λ =35, 50, and 70 μm) and two-mode perturbations (wavelength λ =35 and 70 μm, in phase or in opposite phase). Three-dimensional pattern growth is also compared with the 2D case. Finally the case of the feedthrough mechanism is addressed with rear-side modulated foils.

  14. Indirect drive ablative Rayleigh-Taylor experiments with rugby hohlraums on OMEGA

    International Nuclear Information System (INIS)

    Casner, A.; Galmiche, D.; Huser, G.; Jadaud, J.-P.; Liberatore, S.; Vandenboomgaerde, M.

    2009-01-01

    Results of ablative Rayleigh-Taylor instability growth experiments performed in indirect drive on the OMEGA laser facility [T. R. Boehly, D. L. Brown, S. Craxton et al., Opt. Commun. 133, 495 (1997)] are reported. These experiments aim at benchmarking hydrocodes simulations and ablator instabilities growth in conditions relevant to ignition in the framework of the Laser MegaJoule [C. Cavailler, Plasma Phys. Controlled Fusion 47, 389 (2005)]. The modulated samples under study were made of germanium-doped plastic (CHGe), which is the nominal ablator for future ignition experiments. The incident x-ray drive was provided using rugby-shaped hohlraums [M. Vandenboomgaerde, J. Bastian, A. Casner et al., Phys. Rev. Lett. 99, 065004 (2007)] and was characterized by means of absolute time-resolved soft x-ray power measurements through a dedicated diagnostic hole, shock breakout data and one-dimensional and two-dimensional (2D) side-on radiographies. All these independent x-ray drive diagnostics lead to an actual on-foil flux that is about 50% smaller than laser-entrance-hole measurements. The experimentally inferred flux is used to simulate experimental optical depths obtained from face-on radiographies for an extensive set of initial conditions: front-side single-mode (wavelength λ=35, 50, and 70 μm) and two-mode perturbations (wavelength λ=35 and 70 μm, in phase or in opposite phase). Three-dimensional pattern growth is also compared with the 2D case. Finally the case of the feedthrough mechanism is addressed with rear-side modulated foils.

  15. Detailed Measurements of Rayleigh-Taylor Mixing at Large and Small Atwood Numbers

    International Nuclear Information System (INIS)

    Malcolm, J.; Andrews, Ph.D.

    2004-01-01

    This project has two major tasks: Task 1. The construction of a new air/helium facility to collect detailed measurements of Rayleigh-Taylor (RT) mixing at high Atwood number, and the distribution of these data to LLNL, LANL, and Alliance members for code validation and design purposes. Task 2. The collection of initial condition data from the new Air/Helium facility, for use with validation of RT simulation codes at LLNL and LANL. Also, studies of multi-layer mixing with the existing water channel facility. Over the last twelve (12) months there has been excellent progress, detailed in this report, with both tasks. As of December 10, 2004, the air/helium facility is now complete and extensive testing and validation of diagnostics has been performed. Currently experiments with air/helium up to Atwood numbers of 0.25 (the maximum is 0.75, but the highest Reynolds numbers are at 0.25) are being performed. The progress matches the project plan, as does the budget, and we expect this to continue for 2005. With interest expressed from LLNL we have continued with initial condition studies using the water channel. This work has also progressed well, with one of the graduate Research Assistants (Mr. Nick Mueschke) visiting LLNL the past two summers to work with Dr. O. Schilling. Several journal papers are in preparation that describe the work. Two MSc.'s have been completed (Mr. Nick Mueschke, and Mr. Wayne Kraft, 12/1/03). Nick and Wayne are both pursuing Ph.D.s' funded by this DOE Alliances project. Presently three (3) Ph.D. graduate Research Assistants are supported on the project, and two (2) undergraduate Research Assistants. During the year two (2) journal papers and two (2) conference papers have been published, ten (10) presentations made at conferences, and three (3) invited presentations

  16. Detailed Measurements of Turbulent Rayleigh-Taylor Mixing at Large and Small Atwood Numbers

    Energy Technology Data Exchange (ETDEWEB)

    Malcolm J. Andrews, Ph.D.

    2004-12-14

    This project has two major tasks: Task 1. The construction of a new air/helium facility to collect detailed measurements of Rayleigh-Taylor (RT) mixing at high Atwood number, and the distribution of these data to LLNL, LANL, and Alliance members for code validation and design purposes. Task 2. The collection of initial condition data from the new Air/Helium facility, for use with validation of RT simulation codes at LLNL and LANL. Also, studies of multi-layer mixing with the existing water channel facility. Over the last twelve (12) months there has been excellent progress, detailed in this report, with both tasks. As of December 10, 2004, the air/helium facility is now complete and extensive testing and validation of diagnostics has been performed. Currently experiments with air/helium up to Atwood numbers of 0.25 (the maximum is 0.75, but the highest Reynolds numbers are at 0.25) are being performed. The progress matches the project plan, as does the budget, and we expect this to continue for 2005. With interest expressed from LLNL we have continued with initial condition studies using the water channel. This work has also progressed well, with one of the graduate Research Assistants (Mr. Nick Mueschke) visiting LLNL the past two summers to work with Dr. O. Schilling. Several journal papers are in preparation that describe the work. Two MSc.'s have been completed (Mr. Nick Mueschke, and Mr. Wayne Kraft, 12/1/03). Nick and Wayne are both pursuing Ph.D.s' funded by this DOE Alliances project. Presently three (3) Ph.D. graduate Research Assistants are supported on the project, and two (2) undergraduate Research Assistants. During the year two (2) journal papers and two (2) conference papers have been published, ten (10) presentations made at conferences, and three (3) invited presentations.

  17. The feed-out process: Rayleigh-Taylor and Richtmyer-Meshkov instabilities in thin, laser-driven foils

    Energy Technology Data Exchange (ETDEWEB)

    Smitherman, D.P.

    1998-04-01

    Eight beams carrying a shaped pulse from the NOVA laser were focused into a hohlraum with a total energy of about 25 kJ. A planar foil was placed on the side of the hohlraum with perturbations facing away from the hohlraum. All perturbations were 4 {micro}m in amplitude and 50 {micro}m in wavelength. Three foils of pure aluminum were shot with thicknesses and pulse lengths respectively of 86 {micro}m and 2. 2 ns, 50 {micro}m and 4.5 ns, and 35 {micro}m with both 2.2 ns and 4. 5 ns pulses. Two composite foils constructed respectively of 32 and 84 {micro}m aluminum on the ablative side and 10 {micro}m beryllium on the cold surface were also shot using the 2.2 ns pulse. X-ray framing cameras recorded perturbation growth using both face- and side-on radiography. The LASNEX code was used to model the experiments. A shock wave interacted with the perturbation on the cold surface generating growth from a Richtmyer-Meshkov instability and a strong acoustic mode. The cold surface perturbation fed-out to the Rayleigh-Taylor unstable ablation surface, both by differential acceleration and interface coupling, where it grew. A density jump did not appear to have a large effect on feed-out from interface coupling. The Rayleigh-Taylor instability`s vortex pairs overtook and reversed the direction of flow of the Richtmyer-Meshkov vortices, resulting in the foil moving from a sinuous to a bubble and spike configuration. The Rayleigh-Taylor instability may have acted as an ablative instability on the hot surface, and as a classical instability on the cold surface, on which grew second and third order harmonics.

  18. Observed transition from Richtmyer-Meshkov jet formation through feedout oscillations to Rayleigh-Taylor instability in a laser target

    International Nuclear Information System (INIS)

    Aglitskiy, Y.; Karasik, M.; Velikovich, A. L.; Serlin, V.; Weaver, J. L.; Kessler, T. J.; Schmitt, A. J.; Obenschain, S. P.; Nikitin, S. P.; Oh, J.; Metzler, N.

    2012-01-01

    Experimental study of hydrodynamic perturbation evolution triggered by a laser-driven shock wave breakout at the free rippled rear surface of a plastic target is reported. At sub-megabar shock pressure, planar jets manifesting the development of the Richtmyer-Meshkov-type instability in a non-accelerated target are observed. As the shock pressure exceeds 1 Mbar, an oscillatory rippled expansion wave is observed, followed by the “feedout” of the rear-surface perturbations to the ablation front and the development of the Rayleigh-Taylor instability, which breaks up the accelerated target.

  19. Formation of large-scale structures with sharp density gradient through Rayleigh-Taylor growth in a two-dimensional slab under the two-fluid and finite Larmor radius effects

    International Nuclear Information System (INIS)

    Goto, R.; Hatori, T.; Miura, H.; Ito, A.; Sato, M.

    2015-01-01

    Two-fluid and the finite Larmor effects on linear and nonlinear growth of the Rayleigh-Taylor instability in a two-dimensional slab are studied numerically with special attention to high-wave-number dynamics and nonlinear structure formation at a low β-value. The two effects stabilize the unstable high wave number modes for a certain range of the β-value. In nonlinear simulations, the absence of the high wave number modes in the linear stage leads to the formation of the density field structure much larger than that in the single-fluid magnetohydrodynamic simulation, together with a sharp density gradient as well as a large velocity difference. The formation of the sharp velocity difference leads to a subsequent Kelvin-Helmholtz-type instability only when both the two-fluid and finite Larmor radius terms are incorporated, whereas it is not observed otherwise. It is shown that the emergence of the secondary instability can modify the outline of the turbulent structures associated with the primary Rayleigh-Taylor instability

  20. An Experimental Study of the Turbulent Development of Rayleigh-Taylor and Richtmyer-Meshkov Instabilities

    International Nuclear Information System (INIS)

    Jacobs, Jeffrey W.

    2006-01-01

    The objective of this three-year research program is to study the development of turbulence in Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities. Incompressible RT and RM instabilities are studied in an apparatus in which a box containing two unequal density liquids is accelerated on a linear rail system either impulsively (by bouncing it off of a spring) to produce RM instability, or at a constant downward rate (using a weight and pulley system) to produce RT instability. These experiments are distinguished from others in the field in that they are initialized with well defined, measurable initial perturbations and are well visualized utilizing planar laser induced fluorescence imaging. New experiments are proposed aimed at generating fully turbulent RM and RT instabilities and quantifying the turbulent development once fully turbulent flows are achieved. The proposed experiments focus on the development and the subsequent application of techniques to accelerate the production of fully turbulent instabilities and the quantification of the turbulent instabilities once they are achieved. The proposed tasks include: the development of RM and RT experiments utilizing fluid combinations having larger density ratios than those previously used; the development of RM experiments with larger acceleration impulse than that previously used; and the investigation of the multi-mode and three-dimensional instabilities by the development of new techniques for generating short wavelength initial perturbations. Progress towards fulfilling these goals is currently well on track. Recent results have been obtained on experiments that utilize Faraday resonance for the production of a nearly single-mode three-dimensional perturbation with a short enough wavelength to yield a self-similar instability at late-times. Last year we reported that we can reliably generate Faraday internal waves on the interface in our experimental apparatus by oscillating the tank containing the

  1. Experimental characterization of initial conditions and spatio-temporal evolution of a small Atwood number Rayleigh-Taylor mixing layer

    Energy Technology Data Exchange (ETDEWEB)

    Mueschke, N J; Andrews, M J; Schilling, O

    2005-09-26

    The initial multi-mode interfacial velocity and density perturbations present at the onset of a small Atwood number, incompressible, miscible, Rayleigh-Taylor instability-driven mixing layer have been quantified using a combination of experimental techniques. The streamwise interfacial and spanwise interfacial perturbations were measured using high-resolution thermocouples and planar laser-induced fluorescence (PLIF), respectively. The initial multi-mode streamwise velocity perturbations at the two-fluid density interface were measured using particle-image velocimetry (PIV). It was found that the measured initial conditions describe an initially anisotropic state, in which the perturbations in the streamwise and spanwise directions are independent of one another. The evolution of various fluctuating velocity and density statistics, together with velocity and density variance spectra, were measured using PIV and high-resolution thermocouple data. The evolution of the velocity and density statistics is used to investigate the early-time evolution and the onset of strongly-nonlinear, transitional dynamics within the mixing layer. The early-time evolution of the density and vertical velocity variance spectra indicate that velocity fluctuations are the dominant mechanism driving the instability development. The implications of the present experimental measurements on the initialization of Reynolds-averaged turbulent transport and mixing models and of direct and large-eddy simulations of Rayleigh-Taylor instability-induced turbulence are discussed.

  2. Nonlinear stage of Z-pinch instability

    International Nuclear Information System (INIS)

    Garanin, S.F.; Chernyshev, Yu.D.

    1987-01-01

    Nonlinear development of MHD instability of constriction type for Z-pinch with completely skinned current is considered. The two-dimensional numerical calculations of the constriction show that its development enters the stage described by automodel solution, when the constriction length is fixed and plasma compression takes place in an isentropic way. At the perturbation wave length small, as compared with pinch radius, the stage is preceded by a stage reduced to nonlinear Rayleigh-Taylor instability. For that case dynamics of the motion of magnetic field ''bubbles'' and plasma ''jets'' is considered. It is shown that plasma jets escaping from the pinch region do not close the pinch from current source

  3. Investigation of single-mode and multi-mode hydromagnetic Rayleigh-Taylor instability in planar geometry

    International Nuclear Information System (INIS)

    Roderick, N.F.; Cochrane, K.; Douglas, M.R.

    1998-01-01

    Previous investigations carried out to study various methods of seeding the hydromagnetic Rayleigh-Taylor instability in magnetohydrodynamic simulations showed features similar to those seen in hydrodynamic calculations. For periodic single-mode initiations the results showed the appearance of harmonics as the single modes became nonlinear. For periodic multi-mode initiations new modes developed that indicated the presence of mode coupling. The MHD simulations used parameters of the high velocity large radius z-pinch experiments performed in the Z-accelerator at Sandia National Laboratories. The cylindrical convergent geometry and variable acceleration of these configurations made comparison with analytic, developed for planar geometry with constant acceleration, difficult. A set of calculations in planar geometry using constant current to produce acceleration and parameters characteristic of the cylindrical implosions has been performed to allow a better comparison. Results of these calculations, comparison with analytic theory, and comparison with the cylindrical configuration calculations will be discussed

  4. Experimental Measurement of the Density Fluctuation PDF for small Atwood, high Schmidt number, Rayleigh-Taylor mixing

    Science.gov (United States)

    Duggleby, Andrew; Doron, Yuval; Andrews, Malcolm

    2008-11-01

    The experimental measurement of the probability density function (pdf) of density fluctuations in a Rayleigh-Taylor small Atwood water channel facility with high Schmidt number is reported. In the experiments, molecular mixing is measured by a phenolphthalein chemical indicator that reacts, turning from transparent to pink, when the heavy (salty & acidic) and light (fresh & alkali) water streams mix together. The degree of molecular mixing is determined from the relationship between amount of the chemical reaction formed and the density variance ρ'^2. By measuring the concentration of the reaction product by backlit optical technique for various initial pH differentials, a detailed pdf of the density fluctuation has been obtained. The shape of the density fluctuation pdf as well as future research will be discussed.

  5. Scaling laws of nonlinear Rayleigh-Taylor and Richtmyer-Meshkov instabilities in two and three dimensions

    International Nuclear Information System (INIS)

    Shvarts, D.; Oron, D.; Kartoon, D.; Rikanati, A.; Sadot, O.; Srebro, Y.; Yedvab, Y.; Ofer, D.; Levin, A.; Sarid, E.; Shvarts, D.; Oron, D.; Kartoon, D.; Rikanati, A.; Sadot, O.; Srebro, Y.; Yedvab, Y.; Ben-Dor, G.; Erez, L.; Erez, G.; Yosef-Hai, A.; Alon, U.; Arazi, L.

    2000-01-01

    The late-time nonlinear evolution of the Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities for random initial perturbations is investigated using a statistical mechanics model based on single-mode and bubble-competition physics at al Atwood numbers (A) and full numerical simulations in two and three dimensions. It is shown that the RT mixing zone bubble and spike fronts evolve as h∼α.A.gt 2 with different values of α for the bubble and spike fronts. The RM mixing zone fronts evolve as h∼θ with different values of θ for bubbles and spikes. Similar analysis yields a linear growth with time of the Kelvin-Helmholtz mixing zone. The dependence of the RT and RM scaling parameters on A and the dimensionality will be discussed. The 3-D predictions are found to be in good agreement with recent Linear Electric Motor (LEM) experiments. (authors)

  6. Rayleigh-Taylor Type Instabilities in the Reconnection Exhaust Jet as a Mechanism for Supra-arcade Downflows in the Sun

    Science.gov (United States)

    Guo, L.-J.; Huang, Y.-M.; Bhattacharjee, A.; Innes, D. E.

    2014-12-01

    Supra-arcade downflows (hereafter referred to as SADs) are low-emission, elongated, finger-like features observed in active region coronae above post-eruption flare arcades. Observations exhibit downward moving SADs intertwined with bright upward growing spikes. Whereas SADs are dark voids, spikes are brighter, denser structures. Although SADs have been observed for more than a decade, the mechanism of the formation of SADs remains an open issue. Using three-dimensional resistive magnetohydrodynamic simulations, we demonstrate that Rayleigh-Taylor-type instabilities develop in the downstream region of a reconnecting current sheet. The instabilities result in the formation of low-density coherent structures that resemble SADs, and high-density structures that appear to be spike-like. Comparison between the simulation results and observations suggests that Rayleigh-Taylor-type instabilities in the exhaust of reconnecting current sheets provide a plausible mechanism for observed SADs.

  7. Multiple eigenmodes of the Rayleigh-Taylor instability observed for a fluid interface with smoothly varying density

    Science.gov (United States)

    Yu, C. X.; Xue, C.; Liu, J.; Hu, X. Y.; Liu, Y. Y.; Ye, W. H.; Wang, L. F.; Wu, J. F.; Fan, Z. F.

    2018-01-01

    In this article, multiple eigen-systems including linear growth rates and eigen-functions have been discovered for the Rayleigh-Taylor instability (RTI) by numerically solving the Sturm-Liouville eigen-value problem in the case of two-dimensional plane geometry. The system called the first mode has the maximal linear growth rate and is just extensively studied in literature. Higher modes have smaller eigen-values, but possess multi-peak eigen-functions which bring on multiple pairs of vortices in the vorticity field. A general fitting expression for the first four eigen-modes is presented. Direct numerical simulations show that high modes lead to appearances of multi-layered spike-bubble pairs, and lots of secondary spikes and bubbles are also generated due to the interactions between internal spikes and bubbles. The present work has potential applications in many research and engineering areas, e.g., in reducing the RTI growth during capsule implosions in inertial confinement fusion.

  8. Dimensionality dependence of the Rayleigh-Taylor and Richtmyer-Meshkov instability late-time scaling laws

    International Nuclear Information System (INIS)

    Oron, D.; Arazi, L.; Kartoon, D.; Rikanati, A.; Alon, U.; Shvarts, D.

    2001-01-01

    The late-time nonlinear evolution of the three-dimensional (3D) Rayleigh-Taylor (RT) and Richtmyer-Meshkov (RM) instabilities for random initial perturbations is investigated. Using full 3D numerical simulations, a statistical mechanics bubble-competition model, and a Layzer-type drag-buoyancy model, it is shown that the RT scaling parameters, α B and α S , are similar in two and three dimensions, but the RM exponents, θ B and θ S are lower by a factor of 2 in three dimensions. The similarity parameter h B / is higher by a factor of 3 in the 3D case compared to the 2D case, in very good agreement with recent Linear Electric Motor (LEM) experiments. A simple drag-buoyancy model, similar to that proposed by Youngs [see J. C. V. Hanson et al., Laser Part. Beams 8, 51 (1990)], but using the coefficients from the A=1 Layzer model, rather than phenomenological ones, is introduced

  9. Hot-spot dynamics and deceleration-phase Rayleigh-Taylor instability of imploding inertial confinement fusion capsules

    International Nuclear Information System (INIS)

    Betti, R.; Umansky, M.; Lobatchev, V.; Goncharov, V.N.; McCrory, R.L.

    2001-01-01

    A model for the deceleration phase of imploding inertial confinement fusion capsules is derived by solving the conservation equations for the hot spot. It is found that heat flux leaving the hot spot goes back in the form of internal energy and pdV work of the material ablated off the inner shell surface. Though the hot-spot temperature is reduced by the heat conduction losses, the hot-spot density increases due to the ablated material in such a way that the hot-spot pressure is approximately independent of heat conduction. For direct-drive National Ignition Facility-like capsules, the ablation velocity off the shell inner surface is of the order of tens μm/ns, the deceleration of the order of thousands μm/ns2, and the density-gradient scale length of the order a few μm. Using the well-established theory of the ablative Rayleigh-Taylor instability, it is shown that the growth rates of the deceleration phase instability are significantly reduced by the finite ablative flow and the unstable spectrum exhibits a cutoff for mode numbers of about l≅90

  10. Three-dimensional simulation of hydrodynamic Rayleigh Taylor instabilities at the ablation front of an ICF target

    Energy Technology Data Exchange (ETDEWEB)

    Deck, D.; Samba, G.; Brouillat, S.; Cherfils, C.; Colombet, L.; Gaiffe, S.; Galmichel, D.; Grospellier, G.; Grospellier, L.; Porcher, T.; Weill, J.C. [CEA Bruyeres-le-Chatel (DIF), 91 (France)

    2003-07-01

    To model ignition for the laser Mega Joule project, it is important to simulate the growth of hydrodynamic instabilities that occur in the implosion of the Inertial Confinement Fusion target. Such instabilities can mix the pusher (CH) and the fuel (DT), consequently degrade the implosion performance and quench the ignition. During the capsule acceleration, the ablation surface is Rayleigh Taylor unstable. The perturbations initially located on the ablator surface grow exponentially during the linear phase and then saturate. The saturation time depends not only on the wavelength of the perturbation but also on its shape. 3D calculations are thus needed to take into account the shapes of realistic perturbations. In this paper, we present results for single mode perturbations similar to those of M.M Marinak and al. The roughness of the ablator is modelled with different rectilinear single mode perturbations of equal wave number. The shape of these perturbations varies from full symmetric 3D squared to 2D asymmetric. (authors)

  11. Effects of temporal density variation and convergent geometry on nonlinear bubble evolution in classical Rayleigh-Taylor instability.

    Science.gov (United States)

    Goncharov, V N; Li, D

    2005-04-01

    Effects of temporal density variation and spherical convergence on the nonlinear bubble evolution of single-mode, classical Rayleigh-Taylor instability are studied using an analytical model based on Layzer's theory [Astrophys. J. 122, 1 (1955)]. When the temporal density variation is included, the bubble amplitude in planar geometry is shown to asymptote to integral(t)U(L)(t')rho(t')dt'/rho(t), where U(L) = square root of (g/(C(g)k)) is the Layzer bubble velocity, rho is the fluid density, and C(g) = 3 and C(g) = 1 for the two- and three-dimensional geometries, respectively. The asymptotic bubble amplitude in a converging spherical shell is predicted to evolve as eta approximately etam(-/r0//(lU(L)sp-eta/r0), where r0 is the outer shell radius, eta(t) = integral(t)U(L)sp(t')rho(t') r(0)2(t')dt'/rho(t)r(0)2(t), U(L)(sp) = square root of (-r0(t)r0(t)/l), m(t) = rho(t)r(0)3(t), and l is the mode number.

  12. Numerical investigation on the effects of acceleration reversal times in Rayleigh-Taylor Instability with multiple reversals

    Science.gov (United States)

    Farley, Zachary; Aslangil, Denis; Banerjee, Arindam; Lawrie, Andrew G. W.

    2017-11-01

    An implicit large eddy simulation (ILES) code, MOBILE, is used to explore the growth rate of the mixing layer width of the acceleration-driven Rayleigh-Taylor instability (RTI) under variable acceleration histories. The sets of computations performed consist of a series of accel-decel-accel (ADA) cases in addition to baseline constant acceleration and accel-decel (AD) cases. The ADA cases are a series of varied times for the second acceleration reversal (t2) and show drastic differences in the growth rates. Upon the deceleration phase, the kinetic energy of the flow is shifted into internal wavelike patterns. These waves are evidenced by the examined differences in growth rate in the second acceleration phase for the set of ADA cases. Here, we investigate global parameters that include mixing width, growth rates and the anisotropy tensor for the kinetic energy to better understand the behavior of the growth during the re-acceleration period. Authors acknowledge financial support from DOE-SSAA (DE-NA0003195) and NSF CAREER (#1453056) awards.

  13. Nonlinear hydromagnetic Rayleigh-Taylor instability for strong viscous fluids in porous media

    CERN Document Server

    El-Dib, Y O

    2003-01-01

    In the present work a weakly nonlinear stability for magnetic fluid is discussed. The research of an interface between two strong viscous homogeneous incompressible fluids through porous medium is investigated theoretically and graphically. The effect of the vertical magnetic field has been demonstrated in this study. The linear form of equation of motion is solved in the light of the nonlinear boundary conditions. The boundary value problem leads to construct nonlinear characteristic equation having complex coefficients in elevation function. The nonlinearity is kept to third-order expansion. The nonlinear characteristic equation leads to derive the well-known nonlinear Schroedinger equation. This equation having complex coefficients of the disturbance amplitude varies in both space and time. Stability criteria have been performed for nonlinear Chanderasekhar dispersion relation including the porous effects. Stability conditions are discussed through the assumption of equal kinematic viscosity. The calculati...

  14. A variable-coefficient unstable nonlinear Schroedinger model for the electron beam plasmas and Rayleigh-Taylor instability in nonuniform plasmas: Solutions and observable effects

    International Nuclear Information System (INIS)

    Gao Yitian; Tian Bo

    2003-01-01

    A variable-coefficient unstable nonlinear Schroedinger model is hereby investigated, which arises in such applications as the electron-beam plasma waves and Rayleigh-Taylor instability in nonuniform plasmas. With computerized symbolic computation, families of exact analytic dark- and bright-soliton-like solutions are found, of which some previously published solutions turn out to be the special cases. Similarity solutions also come out, which are expressible in terms of the elliptic functions and the second Painleve transcendent. Some observable effects caused by the variable coefficient are predicted, which may be detected in the future with the relevant space or laboratory plasma experiments with nonuniform background existing

  15. Experimental study of the initial conditions of the Rayleigh-Taylor instability at the ablation front in inertial confinement fusion

    International Nuclear Information System (INIS)

    Delorme, Barthelemy

    2015-01-01

    Numerous designs and experiments in the domain of Inertial Confinement Fusion (ICF) show that, in both direct and indirect drive approaches, one of the main limitations to reach the ignition is the Rayleigh-Taylor instability (RTI). It may lead to shell disruption and performance degradation of spherically imploding targets. Thus, the understanding and the control of the initial conditions of the RTI is of crucial importance for the ICF program. In this thesis, we present an experimental and theoretical study of the initial conditions of the ablative RTI in direct drive, by means of two experimental campaigns performed on the OMEGA laser facility (LLE, Rochester). The first campaign consisted in studying the laser-imprinted ablative Richtmyer-Meshkov instability (RMI) which starts at the beginning of the interaction and seeds the ablative RTI. We set up an experimental configuration that allowed to measure for the first time the temporal evolution of the laser-imprinted ablative RMI. The experimental results have been interpreted by a theoretical model and numerical simulations performed with the hydrodynamic code CHIC. We show that the best way to control the ablative RMI is to reduce the laser intensity inhomogeneities. This can be achieved with targets covered by a layer of a low density foam. Thus, in the second campaign, we studied for the first time the effect of underdense foams on the growth of the ablative RTI. A layer of low density foam was placed in front of a plastic foil, and the perturbation was imprinted by an intensity modulated laser beam. Experimental data are presented: backscattered laser energy, target dynamic obtained by side-on self emission measurement, and face-on radiographs showing the effect of the foams on the target areal density modulations. These data were interpreted using the CHIC code and the laser-plasma interaction code PARAX. We show that the foams noticeably reduce the amplitude of the laser intensity inhomogeneities and the

  16. Numerical study and modeling of hydrodynamic instabilities in the context of inertial confinement fusion in the presence of self-generated magnetic fields

    International Nuclear Information System (INIS)

    Levy, Y.

    2012-01-01

    In the context of inertial confinement fusion we investigate effects of magnetic fields on the development in the linear regime of two hydrodynamic instabilities: Richtmyer-Meshkov instability using ideal magnetohydrodynamics and ablative Rayleigh-Taylor instability in both acceleration and deceleration stages. Direct numerical simulations with a linear perturbation code enable us to confirm the stabilizing effect of the component of the magnetic field along the perturbations wave vector. The amplitude doesn't grow linearly in time but experiences oscillations instead. The compressibility taken into account in the code does not affect predictions given by an already existing impulsive and incompressible model. As far as Rayleigh-Taylor instability is concerned we study the effects of self-generated magnetic fields that arise from the development of the instability itself. In the acceleration stage we perform two dimensional simulations in planar geometry. We show that magnetic fields of about 1 T can be generated and that the instability growth transits more rapidly into nonlinear growth with the enhancement of the development of the third harmonic. We also propose an adaptation of an existing model that aims at studying thermal conductivity anisotropy effects, to take into account the effects of the self-generated magnetic fields on the Rayleigh-Taylor instability growth rate. Finally, in the deceleration stage, we perform two dimensional simulations in cylindrical geometry that take into account self-generation of magnetic fields due to the instability development. It reveals magnetic fields of about several thousands of Teslas that are not strong enough though to affect the instability behavior. (author) [fr

  17. Secondary Rayleigh-Taylor Instabilities in the Reconnection Exhaust Jet: A Mechanism for Supra-Arcade Downflows in the Solar Corona

    Science.gov (United States)

    Guo, L.; Bhattacharjee, A.; Huang, Y. M.; Innes, D.

    2014-12-01

    Supra-arcade downflows (hereafter referred to as SADs) are low-emission, elongated, finger-like features usually observed in active-region coronae above post-eruption flare arcades. Observations exhibit downward moving SADs intertwined with bright, upward moving spikes. Whereas SADs are dark voids, spikes are brighter, denser structures. Although SADs have been observed for decades, the mechanism for formation of SADs remains an open issue. Using high-Lundquist-number three-dimensional resistive MHD simulations, we demonstrate that secondary Rayleigh-Taylor type instabilities develop in the downstream region of a reconnecting current sheet. The instability results in the formation of low-density coherent structures that resemble SADs, intertwined with high-density structures that appear to be spike-like. Using SDO/AIA images, we highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with siumlations suggest that secondary Rayleigh-Taylor type instabilities in the exhaust of reconnecting current sheets provide a plausible mechanism for observed SADs and spikes. Although the plasma conditions are vastly different, analogous phenomena also occur in the Earth's magnetotail during reconnection.

  18. A propagator matrix method for the Rayleigh-Taylor instability of multiple layers: a case study on crustal delamination in the early Earth

    Science.gov (United States)

    Mondal, Puskar; Korenaga, Jun

    2018-03-01

    The dispersion relation of the Rayleigh-Taylor instability, a gravitational instability associated with unstable density stratification, is of profound importance in various geophysical contexts. When more than two layers are involved, a semi-analytical technique based on the biharmonic formulation of Stokes flow has been extensively used to obtain such dispersion relation. However, this technique may become cumbersome when applied to lithospheric dynamics, where a number of layers are necessary to represent the continuous variation of viscosity over many orders of magnitude. Here, we present an alternative and more efficient method based on the propagator matrix formulation of Stokes flow. With this approach, the original instability problem is reduced to a compact eigenvalue equation whose size is solely determined by the number of primary density contrasts. We apply this new technique to the stability of the early crust, and combined with the Monte Carlo sensitivity analysis, we derive an empirical formula to compute the growth rate of the Rayleigh-Taylor instability for this particular geophysical setting. Our analysis indicates that the likelihood of crustal delamination hinges critically on the effective viscosity of eclogite.

  19. Development of surface perturbation target and thin silicon foil target used to research Rayleigh-Taylor instability in inertial confinement fusion experiment

    International Nuclear Information System (INIS)

    Zhou Bin; Sun Qi; Huang Yaodong; Shen Jun; Wu Guangming; Wang Jue

    2004-01-01

    The developments of the surface perturbation target and the thin silicon foil target used to research Rayleigh-Taylor instability in the resolved experiments of Inertial Confinement Fusion (ICF) are carried out. Based on the laser interference process combined with the figure-transfer process, the surface perturbation target with sine modulated perturbation is gotten, the wavelength is in the range of 20-100 μm and the amplitude is several micrometers. The thin silicon foil within the thickness about 3-4 μm is prepared by semiconductor process together with heavy-doped self-stop etching. Combined with ion beam etching, the check or the stripe patterns are transferred to the surface of thin silicon foils, and then the silicon grating foil is obtained

  20. Nonlinear stage of a Z-pinch instability

    International Nuclear Information System (INIS)

    Garanin, S.F.; Chernyshev, Y.D.

    1987-01-01

    The nonlinear evolution of the sausage instability is analyzed for a Z-pinch with a fully developed skin effect in the current. Two-dimensional numerical calculations carried out on the sausage instability show that its occurrence leads to a stage describable by a self-similar solution when the length of the neck is fixed and the plasma compression is isentropic. At a perturbation wavelength small in comparison with the pinch radius, this stage is preceded by a stage which reduces to a nonlinear Rayleigh--Taylor instability. The dynamics of the motion of magnetic field ''bubbles'' and of plasma ''jets'' is analyzed in this case. The plasma jets emerging from the pinch do not block the pinch from the current source

  1. An experimental study of turbulent mixing by Rayleigh-Taylor instabilities and a two-fluid model of the mixing phenomena

    International Nuclear Information System (INIS)

    Andrews, M.J.

    1992-01-01

    A simple experiment has been used to quantitatively investigate turbulent mixing at an unstable interface when the interface is subject to a large two-dimensional disturbance. The introduction of a small amplitude long wavelength does little to alter the early time development of a planar mixed region, but at late times causes a large overturning motion that tends to thin the planar mixed region and accelerate the overall mixing process. Data have been collected from the experiment by way of image analysis of experimental photographs. These data serve as a source of information for the development of a open-quotes two-fluidclose quotes model of the mixing process. A open-quotes two-fluidclose quotes model has been developed to describe the turbulent mixing by Rayleigh-Taylor instabilities of the two different density fluids investigated in the experimental study above. A one-dimensional model was employed for the planar mixing experiments; here attention is focused on the development of a physically plausible equation to describe the length-scale development within the mixed region. The one-dimensional model was then extended to two-dimensions for the overturning experiments, and terms are added to account for thinning of the mixing region at late times. Data collected from the experiments are used to validate the model and to determine several model constants. The two-fluid model successfully simulates the experimental results and is recommended for further application to turbulent mixing processes in buoyant environments

  2. Laser imprint reduction with a shaping pulse, oscillatory Richtmyer-Meshkov to Rayleigh-Taylor transition and other coherent effects in plastic-foam targets

    International Nuclear Information System (INIS)

    Metzler, N.; Velikovich, A.L.; Schmitt, A.J.; Karasik, M.; Serlin, V.; Mostovych, A.N.; Obenschain, S.P.; Gardner, J.H.; Aglitskiy, Y.

    2003-01-01

    A substantial reduction of the laser imprint with a short, low-energy 'shaping' laser pulse incident upon a foam-plastic sandwich target prior to the main laser pulse has been demonstrated to be possible [Metzler et al., Phys. Plasmas 9, 5050 (2002)]. Nonuniformity of this shaping pulse, however, produces standing sonic waves in the target. Laser-imprinted seeds for the Rayleigh-Taylor (RT) instability growth then emerge from the interaction of these waves with the strong shock wave launched by the drive laser pulse. Such coherent interaction between different waves and modes perturbed at the same wavelength is shown to be important in a variety of situations relevant to the inertial confinement fusion studies. As an example, an oscillatory transition from the classical Richtmyer-Meshkov shock-interface instability development to the RT growth exhibiting a characteristic phase reversal in a target of finite thickness is described. Another example refers to the feedout mechanism of seeding the perturbations that come from the nonuniformities of the rear (inner) surface of the laser target. The coherent interaction between the strong shock wave from the main laser pulse and the rippled rarefaction wave produced by a low-intensity foot of the pulse produces observable effects, such as an extra phase reversal compared to the case of no foot. Some of these predictions are shown to be consistent with our new experimental results obtained in the feedout geometry on the Nike laser facility [S. P. Obenschain et al. Phys. Plasmas 3, 2098 (1996)

  3. Recent ACE 4 Z-pinch experiments: Long implosion time argon loads, uniform fill versus annular shell distributions and the Rayleigh-Taylor instability problem

    International Nuclear Information System (INIS)

    Coleman, P.; Rauch, J.; Rix, W.; Thompson, J.; Wilson, R.

    1997-01-01

    Hammer (1996) and Velikovich (1996) have discussed ways to mitigate the growth of the magneto-Rayleigh-Taylor (MRT) instability in z-pinch (PRS) implosions. They predict that initial mass distributions more complex than a simple annular shell will reduce instability development. Sanford (1996) reported experimental data showing a benefit for a uniform mass distribution compared to a shell; those tests used ''conventional'' load radii of 2.25 and 1.25 cm respectively, and implosion times under 100 ns. However, the instability problem is expected to grow exponentially as the implosion time, or alternatively the initial radius, increases. Thus we made a comparison of a uniform fill load with a shell but at larger radii, 3.6 and 2.5 cm respectively, and at implosion times well above 100 ns. We see nearly a factor of 10X improvement in peak K-shell power and 2X increase in K-shell yield for the uniform mass load. Hence it appears that suitable tailoring of the imploding mass distribution can significantly limit the instability growth

  4. A review of the ablative stabilization of the Rayleigh-Taylor instability in regimes relevant to Inertial Confinement Region. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Kilkenny, J.D.; Glendinning, S.G.; Haan, S.W. [and others

    1993-12-01

    It has been recognized for many year`s that the most significant limitation of ICF is the Rayleigh-Taylor (R-T) instability. It limits the distance an ablatively driven shell can be moved to several times its initial thickness. Fortunately material flow through the unstable region at velocity v{sub A} reduces the growth rate to {radical}{sub 1+kL}/{sup kg} {minus}{beta}kv{sub A} with {beta} from 2-3. In recent years experiments using both x-ray drive and smoothed laser drive to accelerate foils have confirmed our understanding of the ablative R-T instability in planar geometry. The growth of small initial modulations on the foils is measured for growth factors up to 60 for direct drive and 80 for indirect drive. For x-ray drive large stabilization is evident. After some growth, the instability enters the non-linear phase when mode coupling and saturation are also seen and compare well with modeling. Normalized growth rates for direct drive are measured to be higher, but strategies for reduction by raising the isentrope are being investigated. For direct drive, high spatial frequencies are imprinted from the laser beam and amplified by the R-T instability. Modeling shows an understanding of this ``laser imprinting.``

  5. An analysis of the ``accidental painting'' technique of D.A. Siqueiros: the Rayleigh Taylor instability as a tool to create explosive textures

    Science.gov (United States)

    Zetina, S.; Zenit, R.

    2012-11-01

    In the spring of 1936, the famous Mexican muralist David Alfaro Siqueiros organized an experimental painting workshop in New York: a group of artists focused in developing painting techniques through empirical experimentation of modern and industrial materials and tools. Among the young artists attending the workshop was Jackson Pollock. They tested different lacquers and a number of experimental techniques. One of the techniques, named by Siqueiros as a ``controlled accident,'' consisted in pouring layers of paint of different colors on top of each other. After a brief time, the paint from the lower layer emerged from bottom to top creating a relatively regular pattern of blobs. This technique led to the creation of explosion-inspired textures and catastrophic images. We conducted an analysis of this process. We experimentally reproduced the patterns ``discovered'' by Siquieros and analyzed the behavior of the flow. We found that the flow is driven by the well-known Rayleigh Taylor instability: different colors paints have different densities; a heavy layer on top of a light one is an unstable configuration. The blobs and plumes that result from the instability create the aesthetically pleasing patterns. We discuss the importance of fluid mechanics in artistic creation.

  6. Progress on Multicomponent Reynolds-Averaged Navier-Stokes Model Development and Validation for Rayleigh-Taylor and Reshocked Richtmyer-Meshkov Turbulent Mixing

    Science.gov (United States)

    Schilling, Oleg

    2014-11-01

    Recent progress on the development and validation of a new K- ɛ multicomponent Reynolds-averaged Navier-Stokes model is discussed. The model includes mixture molecular dissipation and diffusion terms, molecular and turbulent enthalpy diffusion terms, and models for pressure-dilatation and dilatation dissipation. The model has successfully been applied to a set of ten reshocked Richtmyer-Meshkov mixing experiments, and more recently to experiments with larger Mach numbers and various Atwood numbers. An extension of the model to include a modeled density variance transport equation is described. The three-equation model is applied to various Rayleigh-Taylor mixing cases with complex accelerations. The evolution of various turbulence statistics, fields, and turbulent transport equation budgets are compared among these cases to elucidate differences in the turbulence production, dissipation and diffusion mechanisms. It is also shown that the mechanical turbulence timescale is poorly correlated with the molecular mixing timescale determined by the time-evolution of the molecular mixing parameter. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  7. LAD Early Career Prize Talk:Laboratory astrophysics experiments investigating the effects of high energy fluxes on Rayleigh-Taylor instability growth relevant to young supernova remnants

    Science.gov (United States)

    Kuranz, Carolyn C.; Drake, R. Paul; Park, Hye Sook; Huntington, Channing; Miles, Aaron R.; Remington, Bruce A.; Plewa, Tomek; Trantham, Matt; Shvarts, Dov; Raman, Kumar; MacLaren, Steven; Wan, Wesley; Doss, Forrest; Kline, John; Flippos, Kirk; Malamud, Guy; Handy, Timothy; Prisbey, Shon; Grosskopf, Michael; Krauland, Christine; Klein, Sallee; Harding, Eric; Wallace, Russell; Marion, Donna; Kalantar, Dan

    2017-06-01

    Energy-transport effects can alter the structure that develops as a supernova evolves into a supernova remnant. The Rayleigh Taylor (RT) instability is thought to produce structure at the interface between the stellar ejecta and the circumstellar matter (CSM), based on simple models and hydrodynamic simulations. When a blast wave emerges from an exploding star, it drives a forward shock into the CSM and a reverse shock forms in the expanding stellar ejecta, creating a young supernova remnant (SNR). As mass accumulates in the shocked layers, the interface between these two shocks decelerates, becoming unstable to the RT instability. Simulations predict that RT produces structures at this interface, having a range of spatial scales. When the CSM is dense enough, as in the case of SN 1993J, the hot shocked matter can produce significant radiative fluxes that affect the emission from the SNR. Here we report experimental results from the National Ignition Facility (NIF) to explore how large energy fluxes, which are present in supernovae such as SN 1993J, might affect this structure. The experiment used NIF to create a RT unstable interface subject to a high energy flux by the emergence of a blast wave into lower-density matter, in analogy to the SNR. We also preformed and with a low energy flux to compare the affect of the energy flux on the instability growth. We found that the RT growth was reduced in the experiments with a high energy flux. In analyzing the comparison with SN 1993J, we discovered that the energy fluxes produced by heat conduction appear to be larger than the radiative energy fluxes, and large enough to have dramatic consequences. No reported astrophysical simulations have included radiation and heat conduction self-consistently in modeling SNRs.

  8. Plasma dynamics in a staged pinch device

    International Nuclear Information System (INIS)

    Khattak, N.A.D.; Ahmed, Z.; Mirza, A.M.; Murtaza, G.

    1998-01-01

    Plasma parameters in fiber initiated fast and dense theta-pinch plasma driven by an annular finite-thickness gas-puff Z-pinch are studied. The imploding gas-puff Z-pinch plasma traps an axial magnetic field B/sub z/, compressing it to large values (of the order of several megagauss) in an extremely short time. The rapidly changing magnetic flux of this field induces an azimuthal current on the surface of the coaxially placed fiber, with a rise time an order of magnitude shorter than the applied Z-pinch current. The shorter rise time of the current stabilizes the pinch against sausage mode of MHD instabilities. Our numerical results demonstrate that for a relatively thick gas-puff layer, the compression occurs before the current saturates. At the peak compression the fuel densities of the order of 10/sup 25/ cm/sup -3/ and temperature above 10 keV can be achieved on a time scale of 0.1 nanoseconds, yielding the Lawson Criterion parameters n tau is approximately equal to 10/sup 14/ sec cm/sup -3/ for D-T fuel. The snow-plow effect incorporated in our model exercise a strong influence on the onset and growth rate of sausage and Rayleigh-Taylor (R-T) modes of instabilities. Imposing a rotational velocity on the outer thin gas-puff plasma can control the Rayleigh-Taylor instability. Numerical results indicate that the choice of the spin velocity is critical. Large values of the spin velocity, though provide stabilization against the R-T instability at the final stage of compression, however, it adversely reduce the plasma parameters so essential to achieve controlled fusion. Our analysis, therefore, suggests that a judicious choice of the spin velocity is necessary to obtain the desired temperature and density, especially when we seed D-T fiber plasma with a small fraction of high-Z Kr impurity to initiate the radiative collapse. (author)

  9. On coupled development of MHD instabilities of Rayleigh-Taylor and Kelvin-Helmholtz types in nonuniform gas-plasmas flows

    International Nuclear Information System (INIS)

    Likhachev, A P; Medin, S A

    2010-01-01

    The simultaneous development of the MHD instabilities of Raylegh-Taylor and Kelvin-Helmholtz types at the interface between high-conducting plasmoid and surrounding non- or low-conducting gas is considered. The linear stage of the RTI development is studied analytically for incompressible and compressible fluids. The nonlinear stage of the individual development of the RTI and the coupled development of both instabilities has been investigated numerically. The time-dependent two-dimensional numerical model based on the solution of the Euler gasdynamic equations with body momentum and energy sources of MHD origin has been developed and used in calculations. A disturbance introducing in the background flow has been periodic with varied assignment type and wave length. Fundamental difference between the results of linear and nonlinear analysis has been revealed. In particular, the increment of the RTI development at nonlinear stage is one-two order of magnitude less than that predicted by linear theory and rather weakly depends on initial disturbance mode. In linear analysis the coupled development of the RTI and the KHI is determined by simple summing of the two effects in the expression of wave increment, whereas in nonlinear case the mutual influence of the instabilities leads to essential alterations in their development, main of which is the intensive 'layer-by-layer' destruction of the plasmoid surface.

  10. 3rd year final contractor report for: U.S. Department of Energy Stewardship Science Academic Alliances Program Project Title: Detailed Measurements of Rayleigh-Taylor Mixing at Large and Small Atwood Numbers

    International Nuclear Information System (INIS)

    Malcolm J. Andrews

    2006-01-01

    This project had two major tasks: Task 1. The construction of a new air/helium facility to collect detailed measurements of Rayleigh-Taylor (RT) mixing at high Atwood number, and the distribution of these data to LLNL, LANL, and Alliance members for code validation and design purposes. Task 2. The collection of initial condition data from the new Air/Helium facility, for use with validation of RT simulation codes at LLNL and LANL. This report describes work done in the last twelve (12) months of the project, and also contains a summary of the complete work done over the three (3) life of the project. As of April 1, 2006, the air/helium facility (Task 1) is now complete and extensive testing and validation of diagnostics has been performed. Initial condition studies (Task 2) is also complete. Detailed experiments with air/helium with Atwood numbers up to 0.1 have been completed, and Atwood numbers of 0.25. Within the last three (3) months we have been able to successfully run the facility at Atwood numbers of 0.5. The progress matches the project plan, as does the budget. We have finished the initial condition studies using the water channel, and this work has been accepted for publication on the Journal of Fluid Mechanics (the top fluid mechanics journal). Mr. Nick Mueschke and Mr. Wayne Kraft are continuing with their studies to obtain PhDs in the same field, and will also continue their collaboration visits to LANL and LLNL. Over its three (3) year life the project has supported two(2) Ph.D.'s and three (3) MS's, and produced nine (9) international journal publications, twenty four (24) conference publications, and numerous other reports. The highlight of the project has been our close collaboration with LLNL (Dr. Oleg Schilling) and LANL (Drs. Dimonte, Ristorcelli, Gore, and Harlow)

  11. In search of late time evolution self-similar scaling laws of Rayleigh-Taylor and Richtmyer-Meshkov hydrodynamic instabilities - recent theorical advance and NIF Discovery-Science experiments

    Science.gov (United States)

    Shvarts, Dov

    2017-10-01

    Hydrodynamic instabilities, and the mixing that they cause, are of crucial importance in describing many phenomena, from very large scales such as stellar explosions (supernovae) to very small scales, such as inertial confinement fusion (ICF) implosions. Such mixing causes the ejection of stellar core material in supernovae, and impedes attempts at ICF ignition. The Rayleigh-Taylor instability (RTI) occurs at an accelerated interface between two fluids with the lower density accelerating the higher density fluid. The Richtmyer-Meshkov (RM) instability occurs when a shock wave passes an interface between the two fluids of different density. In the RTI, buoyancy causes ``bubbles'' of the light fluid to rise through (penetrate) the denser fluid, while ``spikes'' of the heavy fluid sink through (penetrate) the lighter fluid. With realistic multi-mode initial conditions, in the deep nonlinear regime, the mixing zone width, H, and its internal structure, progress through an inverse cascade of spatial scales, reaching an asymptotic self-similar evolution: hRT =αRT Agt2 for RT and hRM =αRM tθ for RM. While this characteristic behavior has been known for years, the self-similar parameters αRT and θRM and their dependence on dimensionality and density ratio have continued to be intensively studied and a relatively wide distribution of those values have emerged. This talk will describe recent theoretical advances in the description of this turbulent mixing evolution that sheds light on the spread in αRT and θRM. Results of new and specially designed experiments, done by scientists from several laboratories, were performed recently using NIF, the only facility that is powerful enough to reach the self-similar regime, for quantitative testing of this theoretical advance, will be presented.

  12. Magnetic booster fast ignition macron accelerator

    Science.gov (United States)

    Winterberg, F.

    2006-11-01

    A new fast ignition scheme was recently proposed where the ignition is done by the impact of a small solid projectile accelerated to velocities in excess of 108cm/s, with the acceleration done in two steps: first, by laser ablation of a flyer plate, and second by injecting the flyer plate into a conical duct. The two principal difficulties of this scheme are as follows: first, the required large mass ratio for the laser ablation rocket propelled flyer plate, and second, the Rayleigh-Taylor instability of the flyer plate during its implosive compression in the conical duct. To overcome these difficulties, it is suggested to accelerate a projectile by a magnetic fusion booster stage, made up of a dense, wall-confined magnetized plasma brought to thermonuclear temperatures. After ignition, this plasma undergoes a thermonuclear excursion greatly increasing its pressure, resulting in the explosion of a weakened segment of the wall, with the segment becoming a fast moving projectile. The maximum velocity this projectile can reach is the velocity of sound of the booster stage plasma, which at a temperature of 108K is of the order 108cm/s.

  13. Magnetic booster fast ignition macron accelerator

    International Nuclear Information System (INIS)

    Winterberg, F.

    2006-01-01

    A new fast ignition scheme was recently proposed where the ignition is done by the impact of a small solid projectile accelerated to velocities in excess of 10 8 cm/s, with the acceleration done in two steps: first, by laser ablation of a flyer plate, and second by injecting the flyer plate into a conical duct. The two principal difficulties of this scheme are as follows: first, the required large mass ratio for the laser ablation rocket propelled flyer plate, and second, the Rayleigh-Taylor instability of the flyer plate during its implosive compression in the conical duct. To overcome these difficulties, it is suggested to accelerate a projectile by a magnetic fusion booster stage, made up of a dense, wall-confined magnetized plasma brought to thermonuclear temperatures. After ignition, this plasma undergoes a thermonuclear excursion greatly increasing its pressure, resulting in the explosion of a weakened segment of the wall, with the segment becoming a fast moving projectile. The maximum velocity this projectile can reach is the velocity of sound of the booster stage plasma, which at a temperature of 10 8 K is of the order 10 8 cm/s

  14. Evolution of sausage and helical modes in magnetized thin-foil cylindrical liners driven by a Z-pinch

    Science.gov (United States)

    Yager-Elorriaga, D. A.; Lau, Y. Y.; Zhang, P.; Campbell, P. C.; Steiner, A. M.; Jordan, N. M.; McBride, R. D.; Gilgenbach, R. M.

    2018-05-01

    In this paper, we present experimental results on axially magnetized (Bz = 0.5 - 2.0 T), thin-foil (400 nm-thick) cylindrical liner-plasmas driven with ˜600 kA by the Michigan Accelerator for Inductive Z-Pinch Experiments, which is a linear transformer driver at the University of Michigan. We show that: (1) the applied axial magnetic field, irrespective of its direction (e.g., parallel or anti-parallel to the flow of current), reduces the instability amplitude for pure magnetohydrodynamic (MHD) modes [defined as modes devoid of the acceleration-driven magneto-Rayleigh-Taylor (MRT) instability]; (2) axially magnetized, imploding liners (where MHD modes couple to MRT) generate m = 1 or m = 2 helical modes that persist from the implosion to the subsequent explosion stage; (3) the merging of instability structures is a mechanism that enables the appearance of an exponential instability growth rate for a longer than expected time-period; and (4) an inverse cascade in both the axial and azimuthal wavenumbers, k and m, may be responsible for the final m = 2 helical structure observed in our experiments. These experiments are particularly relevant to the magnetized liner inertial fusion program pursued at Sandia National Laboratories, where helical instabilities have been observed.

  15. Analysis of staged Z-pinch implosion trajectories from experiments on Zebra

    Science.gov (United States)

    Ross, Mike P.; Conti, F.; Darling, T. W.; Ruskov, E.; Valenzuela, J.; Wessel, F. J.; Beg, F.; Narkis, J.; Rahman, H. U.

    2017-10-01

    The Staged Z-pinch plasma confinement concept relies on compressing an annular liner of high-Z plasma onto a target plasma column of deuterium fuel. The interface between the liner and target is stable against the Magneto-Rayleigh-Taylor Instability, which leads to effective fuel compression and makes the concept interesting as a potential fusion reactor. The liner initiates as a neutral gas puff, while the target plasma is a partially ionized (Zeff coaxial plasma gun. The Zebra pulsed power generator (1 MA peak current, 100 ns rise time) provides the discharge that ionizes the liner and drives the Z-pinch implosion. Diverse diagnostics observe the 100-300 km/s implosions including silicon diodes, photo-conducting detectors (PCDs), laser shadowgraphy, an XUV framing camera, and a visible streak camera. The imaging diagnostics track instabilities smaller than 0.1 mm, and Z-pinch diameters below 2.5 mm are seen at peak compression. This poster correlates the data from these diagnostics to elucidate implosion behavior dependencies on liner gas, liner pressure, target pressure, and applied, axial-magnetic field. Funded by the Advanced Research Projects Agency - Energy, DE-AR0000569.

  16. Dual-stage trapped-flux magnet cryostat for measurements at high magnetic fields

    Science.gov (United States)

    Islam, Zahirul; Das, Ritesh K.; Weinstein, Roy

    2015-04-14

    A method and a dual-stage trapped-flux magnet cryostat apparatus are provided for implementing enhanced measurements at high magnetic fields. The dual-stage trapped-flux magnet cryostat system includes a trapped-flux magnet (TFM). A sample, for example, a single crystal, is adjustably positioned proximate to the surface of the TFM, using a translation stage such that the distance between the sample and the surface is selectively adjusted. A cryostat is provided with a first separate thermal stage provided for cooling the TFM and with a second separate thermal stage provided for cooling sample.

  17. Oral cancer staging established by magnetic resonance imaging

    Directory of Open Access Journals (Sweden)

    Rogério Ribeiro de Paiva

    2011-12-01

    Full Text Available The aim of this study was to compare clinical staging and magnetic resonance imaging (MRI staging for oral cancer, and to assess inter-observer agreement between oral and medical radiologists. A total of 10 patients diagnosed with oral cancer were assessed before treatment. A head and neck surgeon performed clinical TNM staging. Two medical radiologists and two oral radiologists performed a new staging assessment by interpreting MRI scans, without prior knowledge of the clinical staging. They evaluated the extent of the primary tumor (T, metastasis to regional lymph nodes (N and grouping by stages. The data were analyzed using the Kappa Index. There was significant agreement (p < 0.05 between the clinical and MRI staging assessments made by one oral radiologist for N stage, and between those made by one medical radiologist for the T and N stages and for the grouping by stages. In the MRI assessment, there was significant agreement among all four observers for both T stage and grouping by stages. For the N stage, there was no significant agreement between one oral radiologist and one medical radiologist or between both medical radiologists. There was significant agreement among the remaining radiologists. There was no agreement between the clinical and MRI staging. These results indicate the importance of using MRI for the diagnosis of oral cancer. Training initiatives and calibration of medical and oral radiologists should be promoted to provide an improved multidisciplinary approach to oral cancer.

  18. Precision Magnetic Bearing Six Degree of Freedom Stage

    Science.gov (United States)

    Williams, M. E.; Trumper, David L.

    1996-01-01

    Magnetic bearings are capable of applying force and torque to a suspended object without rigidly constraining any degrees of freedom. Additionally, the resolution of magnetic bearings is limited only by sensors and control, and not by the finish of a bearing surface. For these reasons, magnetic bearings appear to be ideal for precision wafer positioning in lithography systems. To demonstrate this capability a linear magnetic bearing has been constructed which uses variable reluctance actuators to control the motion of a 14.5 kg suspended platen in five degrees of freedom. A Lorentz type linear motor of our own design and construction is used to provide motion and position control in the sixth degree of freedom. The stage performance results verify that the positioning requirements of photolithography can be met with a system of this type. This paper describes the design, control, and performance of the linear magnetic bearing.

  19. Breakeven Fusion in Staged Z Pinch

    Science.gov (United States)

    Rahman, Hafiz; Ney, Paul; Rostoker, Norman; Wessel, Frank

    2008-03-01

    We are studying the prospect for breakeven thermonuclear fusion considering a Mega joule (MJ) class, 100 ns, impulse generator using a modified version of MACH2, a 2-1/2 D, radiation-code. The load is a cylindrical, xenon plasma shell that implodes radially onto a co-axial, deuterium-tritium plasma target. Optimized plasma density and pinch radius lead to a fusion-energy output that is many times the stored capacitor bank energy. In this ``Staged Z-pinch'' shock fronts form that preheat the DT plasma to several hundred eV, before adiabatic compression. During compression, the Xe liner becomes Rayleigh-Taylor (RT) unstable while the DT target remains stable. Proper selection of the initial pinch radius and plasma density is crucial for optimum implosion efficiency.

  20. Multimode modelling of the Rayleigh-Taylor instability

    International Nuclear Information System (INIS)

    Town, R.P.J.; Findlay, J.D.; Bell, A.R.

    1996-01-01

    This paper presents a comparison of Haan's mode coupling model with two-dimensional hydrocode simulations. In the light of these results, a new saturation criterion is developed that is used in a new, extended mode coupling model. The new extended model accurately follows the mode development to amplitudes 2 to 3 times larger than Haan's model. (Author)

  1. Estimates of molecular mixing in confined Rayleigh-Taylor instability

    Science.gov (United States)

    Lawrie, Andrew; Dalziel, Stuart

    2012-11-01

    We examine the behaviour of a system in which a RT unstable interface is confined between stable continuous stratifications. Recent experiments with linear stratifications (Lawrie & Dalziel 2011, JFM) indicate an intrinsic limit to a fluid's ability to mix, which here can be measured robustly between quiescent initial and final states. Standard incompressible ILES does not match well because it cannot respect the balance of energy conversions observed in experiment. ILES operates with Sc=O(1), whereas Sc=700 in our experiments. Lawrie & Dalziel detailed the relation between the p.d.f. of the density field and the availability of energy in the system. Here we extract the evolution of the p.d.f. over the life-cycle of the instability, and thus quantify the ILES mixing estimates in both 2D and 3D RT cases. In 3D, energy cascades to small scales, so the stretching of material surfaces that it induces tends to occur at comparable scales and this is the optimal condition for doing mixing. In 2D, however, energy accumulates at large scales and thus material surfaces do not become so rapidly stretched. We view the 2D case as an analogue for high Schmidt number behaviour, and this helps us understand the modelling approximations in 3D cases.

  2. 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

  3. Staging of nasopharyngeal carcinoma investigated by magnetic resonance imaging

    International Nuclear Information System (INIS)

    Lu Jincheng; Wei Baoqing; Chen Wenzhan; Qian Pudong; Zhang Yiqin; Wei Qing; Cha Wenwu; Li Feng; Ni Ming

    2006-01-01

    Background and purpose: To investigate the American Joint Commission on Cancer (AJCC) sixth edition staging system of nasopharyngeal carcinoma (NPC) by Magnetic Resonance Imaging (MRI). Patients and methods: One hundred and fifty-nine non-disseminated biopsy-proven NPC patients were studied with MRI before treatment. Retrieval of MRI information enabled us to restage all patients accurately according to the sixth edition of the AJCC staging system. Splitting the respective T and N stages by the significant defining factors identified, the cancer death hazard ratios were modeled by the Cox model in SPSS 10.0 for windows (SPSS Inc, Chicago, IL). Results: Single site of skull base abnormality (HR=3.91, 95% CI: 0.74-20.56) has a superior result to others involved in T3 (HR=5.83, 95% CI: 1.24-27.29). Involvement of either anterior or posterior cranial nerves solely (HR=6.02, 95% CI: 1.55-35.60) was not found to be as a poor prognostic indicator as others involved in T4 (HR=7.81, 95% CI: 1.81-33.63). Less than or equal to 3 cm of N1 (HR=4.01, 95% CI: 0.48-33.83) and N2 (HR=4.72, 95% CI: 0.62-35.78) have a better result than >3 cm of N1 (HR=8.09, 95% CI: 0.95-68.97) and N2 (HR=10.58, 95% CI: 1.32-84.62), respectively. Conclusions: Perhaps, it is better to down-stage single site of skull base abnormality from T3 to T2, and involvement of either anterior or posterior cranial nerves solely from T4 to T3, meanwhile, ≤3 cm of N2 down-stage to N1, >3 cm of N1 up-stage to N2

  4. Low-Convergence Magnetized Liner Inertial Fusion

    Science.gov (United States)

    Slutz, Stephen; Vesey, Roger; Sinars, Daniel; Sefkow, Adam

    2013-10-01

    Numerical simulations indicate that pulsed-power driven liner-implosions could produce substantial fusion yields if the deuterium-tritium (DT) fuel is first magnetized and preheated [S.A. Slutz et al., Phys. Plasmas 17, 056303 (2010)]. As with all inertial fusion, the implosions could be degraded by the Rayleigh-Taylor instability. Since highly convergent implosions are more susceptible to this instability, we have explored the necessary conditions to obtain significant fusion yield with low-convergence liner-implosions. Such low-convergence implosions can be obtained if the fuel is sufficiently preheated and magnetized. We present analytic and numerical studies of laser plasma heating, which indicate that low convergence implosions should be possible with sufficient laser energy. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contra.

  5. Three-stage linear, split-Stirling cryocooler for 1 to 2K magnetic cold stage

    International Nuclear Information System (INIS)

    Longsworth, R.C.

    1993-08-01

    A long-life, linear, high efficiency 8K split Stirling cycle cryocooler was designed, built, and tested. The refrigerator is designed for cooling a 50 mW, 1.5K magnetic cold stage. Dual opposed piston compressors are driven by moving-coil linear motors. The three stage expander, although not completed, is also driven by a linear motor and is designed to produce 1 SW at 60K, 4W at 16K, and 1.2W at 8K. The cold regenerator employs a parallel gap construction for high efficiency. The key technology areas addressed include warm and cold flexible suspension bearings and a new cold regenerator geometry for high efficiency at 8K

  6. Uterine cervical cancer. Preoperative staging with magnetic resonance imaging; Zervixkarzinom. Praeoperatives Staging mittels Magnetresonanztomographie

    Energy Technology Data Exchange (ETDEWEB)

    Collettini, F.; Hamm, B. [Charite-Universitaetsmedizin Berlin, Campus Charite Mitte, Klinik fuer Radiologie, Berlin (Germany)

    2011-07-15

    The treatment of uterine cervical carcinoma is largely dependent on the tumor stage. Despite significant inaccuracies in the clinical examination, uterine cervical cancer remains the only gynecological form of cancer still largely staged according to clinical findings. Although imaging is still not included in the staging the recently published revised FIGO (Federation International de Gynecologie et d'Obstetrique) system encourages the use of modern cross-sectional imaging (magnetic resonance imaging MRI and computed tomography CT). Due to its high soft tissue contrast MRI allows excellent non-invasive assessment of the cervix with direct tumor delineation as well as assessment of the prognosis based on morphological factors. Studies in the literature report an accuracy of 93% for MRI in the preoperative assessment of tumor size and in the differentiation of operable from advanced cervical cancer. Therefore MRI is considered to be the optimal modality for diagnostic evaluation starting from FIGO stage IB1, for radiation therapy planning, and for exclusion of recurrence in follow-up. In this paper we give an overview of the role of magnetic resonance imaging in preoperative staging of uterine cervical cancer. (orig.) [German] Die Therapieplanung beim Zervixkarzinom ist weitgehend von der Stadieneinteilung nach FIGO (Federation International de Gynecologie et d'Obstetrique) abhaengig, die trotz erheblicher Ungenauigkeiten bei der klinischen Stadieneinteilung weiterhin aufgrund klinischer Untersuchungsbefunde erfolgt. Obwohl bildgebende Verfahren nach wie vor fuer die Stadieneinteilung nicht vorgesehen sind, wird im kuerzlich erschienen revidierten Stagingsystem der FIGO zum ersten Mal die Verwendung moderner Schnittbilddiagnostik (MRT und CT) befuerwortet. Die MRT ermoeglicht dank ihres hohen Weichteilkontrasts ein ausgezeichnetes nichtinvasives Staging des Zervixkarzinoms mit direkter Tumordarstellung sowie einer Prognoseabschaetzung anhand

  7. Pulsating jet-like structures in magnetized plasma

    Energy Technology Data Exchange (ETDEWEB)

    Goncharov, V. P. [A. M. Obukhov Institute of Atmospheric Physics RAS, 109017 Moscow (Russian Federation); Pavlov, V. I. [UFR des Mathématiques Pures et Appliquées, Univ. Lille, CNRS FRE 3723 - LML, F-59000 Lille (France)

    2016-08-15

    The formation of pulsating jet-like structures has been studied in the scope of the nonhydrostatic model of a magnetized plasma with horizontally nonuniform density. We discuss two mechanisms which are capable of stopping the gravitational spreading appearing to grace the Rayleigh-Taylor instability and to lead to the formation of stationary or oscillating localized structures. One of them is caused by the Coriolis effect in the rotating frames, and another is connected with the Lorentz effect for magnetized fluids. Magnetized jets/drops with a positive buoyancy must oscillate in transversal size and can manifest themselves as “radio pulsars.” The estimates of their frequencies are made for conditions typical for the neutron star's ocean.

  8. Magnetic resonance imaging in acute stage of cerebral ischemia

    International Nuclear Information System (INIS)

    Yamagata, Sen; Kikuchi, Haruhiko; Ihara, Ikuo

    1986-01-01

    The value of the nuclear magnetic resonance image (MRI) was investigated in the acute stage of experimental cerebral ischemia. The MRI system employed was designed for clinical use, and the superconducting magnet was operated at a field strength of 1.5 tesla. Ischemic insult was made by transorbital occlusion of the middle cerebral artery (MCA) permanently in 4 cats and temporarily in 2 cats. After MCA occlusion the regional cerebral blood flow (rCBF) was measured on the affected cortex, and 5 cats with rCBF below 10 ml/100 g/min and one with rCBF over 15 ml/100 g/min were studied. In the permanent occlusion group, MRI was performed every 2 hours from 4 to 12 hours after MCA occlusion and another MRI was carried out 20 min after gadolinium-diethylenetriamine-pentaacetic acid (Gd-DTPA) intravenous administration. The earliest changes were found 6 to 8 hours after MCA occlusion on the spin echo image (repetition time = 1.4 sec, echo time = 70 msec) in 3 cats with severe ischemia. It was postulated that the ischemic lesion could be depicted less than 6 hours on more T 2 -weighted images. The increased intensity area was markedly enhanced with Gd-DTPA 12 hours after occlusion. In the recirculation group, the increased intensity area was observed on enhanced MRI in a cat with recirculation as early as one hour after MCA occlusion, although it was not found on the plain MRI. In the other cat with recirculation after 2 hours' occlusion, definite lesion was found in all parameter images without enhancement. The results suggest that changes in cerebral ischemia can be obtained on the MRI earlier than X-ray computed tomography, and that it may be possible to determine the severity of the ischemic brain injury by the MRI findings. (author)

  9. Magnetic resonance imaging in chronic subdural hematomas of early stages

    Energy Technology Data Exchange (ETDEWEB)

    Tsuchiya, Naoto; Muraki, Masaaki; Ohishi, Haruyuki (Shinshiro Municipal Hospital, Aichi (Japan)); Ninchoji, Toshiaki; Uemura, Kenichi

    1990-10-01

    The characteristic findings to distinguish chronic subdural hematomas of early stages from subdural CSF collections or enlarged subarachnoid spaces, was assessed by magnetic resonance imagings (MRI). Three sets of MRI, pre- and post-contrast as well as delayed post-contrast T{sub 1}-weighted coronal images were obtained in 20 cases, in which low intensity subdural spaces were observed in 6 on the right, in 5 on the left and 9 bilaterally. The characteristic findings observed were as follows: a low signal intensity band between low intensity subdural space and cerebral surface at the precontrast MRI; linear enhancement at the outer surface of low intensity space at postcontrast MRI; and enhancement of the low intensity space at the delayed MRI. A combination of more than 2 of the above-mentioned findings was noted in 24 out of 29 low intensity spaces, 7 of which were confirmed by surgery as chronic subdural hematomas with outer membranes. In the remaining 17, low intensity spaces spontaneously regressed in 10, and increased their intensity and/or changed their sizes in 7. This data was obtained from follow-up MRI's. Such a combination in the initial MRI's may indicate developing chronic subdural hematomas. In 5 out of 29 low intensity spaces, neither intensity nor size changed, nor did enhancement show in delayed imagings in the follow-up MRI's, which may strongly suggest either subdural CSF collections or enlarged subarachnoid spaces. In conclusion, the low intensity band is speculated to be subarachnoid space shown up secondarily by the relative increase of intensity in the low intensity space; the linear enhancement is thought to be outer membrane formation, and the delayed-enhancement of low intensity spaces may be extravasation of contrast media from the outer membrane. (author).

  10. Linear Analysis of Converging Richtmyer-Meshkov Instability in the Presence of an Azimuthal Magnetic Field

    KAUST Repository

    Bakhsh, Abeer

    2017-11-17

    We investigate the linear stability of both positive and negative Atwood ratio interfaces accelerated either by a fast magnetosonic or hydrodynamic shock in cylindrical geometry. For the magnetohydrodynamic (MHD) case, we examine the role of an initial seed azimuthal magnetic field on the growth rate of the perturbation. In the absence of a magnetic field, the Richtmyer-Meshkov growth is followed by an exponentially increasing growth associated with the Rayleigh-Taylor instability. In the MHD case, the growth rate of the instability reduces in proportion to the strength of the applied magnetic field. The suppression mechanism is associated with the interference of two waves running parallel and anti-parallel to the interface that transport of vorticity and cause the growth rate to oscillate in time with nearly a zero mean value.

  11. Electrothermal instability growth in magnetically driven pulsed power liners

    International Nuclear Information System (INIS)

    Peterson, Kyle J.; Sinars, Daniel B.; Yu, Edmund P.; Herrmann, Mark C.; Cuneo, Michael E.; Slutz, Stephen A.; Smith, Ian C.; Atherton, Briggs W.; Knudson, Marcus D.; Nakhleh, Charles

    2012-01-01

    This paper explores the role of electro-thermal instabilities on the dynamics of magnetically accelerated implosion systems. Electro-thermal instabilities result from non-uniform heating due to temperature dependence in the conductivity of a material. Comparatively little is known about these types of instabilities compared to the well known Magneto-Rayleigh-Taylor (MRT) instability. We present simulations that show electrothermal instabilities form immediately after the surface material of a conductor melts and can act as a significant seed to subsequent MRT instability growth. We also present the results of several experiments performed on Sandia National Laboratories Z accelerator to investigate signatures of electrothermal instability growth on well characterized initially solid aluminum and copper rods driven with a 20 MA, 100 ns risetime current pulse. These experiments show excellent agreement with electrothermal instability simulations and exhibit larger instability growth than can be explained by MRT theory alone.

  12. Magnetic Reconnection at the Earliest Stage of Solar Flux Emergence

    Science.gov (United States)

    Tian, Hui; Zhu, Xiaoshuai; Peter, Hardi; Zhao, Jie; Samanta, Tanmoy; Chen, Yajie

    2018-02-01

    On 2016 September 20, the Interface Region Imaging Spectrograph observed an active region during its earliest emerging phase for almost 7 hr. The Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory observed continuous emergence of small-scale magnetic bipoles with a rate of ∼1016 Mx s‑1. The emergence of magnetic fluxes and interactions between different polarities lead to the frequent occurrence of ultraviolet (UV) bursts, which exhibit as intense transient brightenings in the 1400 Å images. In the meantime, discrete small patches with the same magnetic polarity tend to move together and merge, leading to the enhancement of the magnetic fields and thus the formation of pores (small sunspots) at some locations. The spectra of these UV bursts are characterized by the superposition of several chromospheric absorption lines on the greatly broadened profiles of some emission lines formed at typical transition region temperatures, suggesting heating of the local materials to a few tens of thousands of kelvin in the lower atmosphere by magnetic reconnection. Some bursts reveal blue- and redshifts of ∼100 km s‑1 at neighboring pixels, indicating the spatially resolved bidirectional reconnection outflows. Many such bursts appear to be associated with the cancellation of magnetic fluxes with a rate of the order of ∼1015 Mx s‑1. We also investigate the three-dimensional magnetic field topology through a magnetohydrostatic model and find that a small fraction of the bursts are associated with bald patches (magnetic dips). Finally, we find that almost all bursts are located in regions of large squashing factor at the height of ∼1 Mm, reinforcing our conclusion that these bursts are produced through reconnection in the lower atmosphere.

  13. Overview of current multiparametric magnetic resonance imaging approach in the diagnosis and staging of prostate cancer

    Directory of Open Access Journals (Sweden)

    Hasan Aydın

    2015-04-01

    Full Text Available This article is primarily based on the utility and validity of multiparametric magnetic resonance imaging in the diagnosis and staging of prostate gland tumors. Multiparametric magnetic resonance imaging is an emerging, useful approach for evaluating and detecting prostate cancers. It also aids in the management of a tumor and improve the care and follow-up of patients.

  14. Can the magnetic field in the Orion arm inhibit the growth of instabilities in the bow shock of Betelgeuse?

    Science.gov (United States)

    van Marle, A. J.; Decin, L.; Meliani, Z.

    2014-01-01

    Context. Many evolved stars travel through space at supersonic velocities, which leads to the formation of bow shocks ahead of the star where the stellar wind collides with the interstellar medium (ISM). Herschel observations of the bow shock of α-Orionis show that the shock is almost free of instabilities, despite being, at least in theory, subject to both Kelvin-Helmholtz and Rayleigh-Taylor instabilities. Aims: A possible explanation for the lack of instabilities lies in the presence of an interstellar magnetic field. We wish to investigate whether the magnetic field of the ISM in the Orion arm can inhibit the growth of instabilities in the bow shock of α-Orionis. Methods: We used the code MPI-AMRVAC to make magneto-hydrodynamic simulations of a circumstellar bow shock, using the wind parameters derived for α-Orionis and interstellar magnetic field strengths of B = 1.4, 3.0, and 5.0 μG, which fall within the boundaries of the observed magnetic field strength in the Orion arm of the Milky Way. Results: Our results show that even a relatively weak magnetic field in the ISM can suppress the growth of Rayleigh-Taylor and Kelvin-Helmholtz instabilities, which occur along the contact discontinuity between the shocked wind and the shocked ISM. Conclusions: The presence of even a weak magnetic field in the ISM effectively inhibits the growth of instabilities in the bow shock. This may explain the absence of such instabilities in the Herschel observations of α-Orionis. Appendix A and associated movies are available in electronic form at http://www.aanda.org

  15. Transrectal ultrasonography and magnetic resonance imaging in the staging of rectal cancer. Effect of experience

    DEFF Research Database (Denmark)

    Rafaelsen, Søren R; Sørensen, Torben; Jakobsen, Anders

    2008-01-01

    OBJECTIVE: To evaluate the effect of experience on preoperative staging of rectal cancer using magnetic resonance imaging (MRI) and transrectal ultrasound (TRUS). MATERIAL AND METHODS: From January 2002 to May 2006, 134 consecutive patients with biopsy-proven rectal cancer were examined with a 1....... In addition to this supervision, the person responsible for staging should be trained through a defined training programme....

  16. A novel Planar Magnetic Bearing and Motor Configuration applied in a Positioning Stage

    NARCIS (Netherlands)

    Molenaar, A.

    2000-01-01

    This thesis presents the design and implementation of a fully contactless high precision magnetically suspended position stage with large planar stroke. This stage is the first which is suitable for practical application in vacuum. The underlying electromechanical working principles, modelling and

  17. How does magnetic resonance imaging influence staging according to AJCC staging system for nasopharyngeal carcinoma compared with computed tomography?

    Science.gov (United States)

    Liao, Xin-Biao; Mao, Yan-Ping; Liu, Li-Zhi; Tang, Ling-Long; Sun, Ying; Wang, Yan; Lin, Ai-Hua; Cui, Chun-Yan; Li, Li; Ma, Jun

    2008-12-01

    To analyze the degree and pattern of influence of magnetic resonance imaging (MRI) on staging according to the 6th edition of the American Joint Committee on Cancer staging system compared with computed tomography (CT). The MRI and CT scans and medical records of 420 consecutive patients with newly diagnosed nasopharyngeal carcinoma (NPC) were analyzed retrospectively. The tumors of all patients were staged according to the 6th edition of the American Joint Committee on Cancer staging system. A significant difference (p <0.05) was found between CT and MRI in demonstrating involvement in the oropharynx (CT, 25.0% vs. MRI, 14.5%), prevertebral muscle (CT, 18.4% vs. MRI, 36.0%), parapharyngeal space (CT, 82.6% vs. MRI, 68.8%), skull base (CT, 31.0% vs. MRI, 52.6%), sphenoid sinus (CT, 13.6% vs. MRI, 16.7%), ethmoid sinus (CT, 7.1% vs. MRI, 3.3%), intracranial area (CT, 4.8% vs. MRI, 16.0%), and retropharyngeal lymph nodes (CT, 52.1% vs. MRI, 69.0%). The incidence of cervical lymph node metastasis and lymph node metastasis at each level was similar according to CT and MRI. MRI resulted in changes in 49.8% of T stage cases, 10.7% of N stage cases, and 38.6% of clinical stage cases. MRI demonstrated early primary tumor involvement more precisely and deep primary tumor infiltration more easily. The use of MRI caused dramatic changes in the results of the T stage and clinical staging and should be preferred to CT in staging NPC. Patients would benefit from changes in treatment strategies resulting from the use of MRI.

  18. Forensic age estimation based on magnetic resonance imaging of third molars: converting 2D staging into 3D staging.

    Science.gov (United States)

    De Tobel, Jannick; Hillewig, Elke; Verstraete, Koenraad

    2017-03-01

    Established methods to stage development of third molars for forensic age estimation are based on the evaluation of radiographs, which show a 2D projection. It has not been investigated whether these methods require any adjustments in order to apply them to stage third molars on magnetic resonance imaging (MRI), which shows 3D information. To prospectively study root stage assessment of third molars in age estimation using 3 Tesla MRI and to compare this with panoramic radiographs, in order to provide considerations for converting 2D staging into 3D staging and to determine the decisive root. All third molars were evaluated in 52 healthy participants aged 14-26 years using MRI in three planes. Three staging methods were investigated by two observers. In sixteen of the participants, MRI findings were compared with findings on panoramic radiographs. Decisive roots were palatal in upper third molars and distal in lower third molars. Fifty-seven per cent of upper third molars were not assessable on the radiograph, while 96.9% were on MRI. Upper third molars were more difficult to evaluate on radiographs than on MRI (p third molars were equally assessable on both imaging techniques (93.8% MRI, 98.4% radiograph), with no difference in level of difficulty (p = .375). Inter- and intra-observer agreement for evaluation was higher in MRI than in radiographs. In both imaging techniques lower third molars showed greater inter- and intra-observer agreement compared to upper third molars. MR images in the sagittal plane proved to be essential for staging. In age estimation, 3T MRI of third molars could be valuable. Some considerations are, however, necessary to transfer known staging methods to this 3D technique.

  19. Magnetic resonance imaging of spinal cord injury in chronic stage

    International Nuclear Information System (INIS)

    Tobimatsu, Haruki; Nihei, Ryuichi; Kimura, Tetsuhiko; Yano, Hideo; Touyama, Tetsuo; Tobimatsu, Yoshiko; Suyama, Naoto; Yoshino, Yasumasa

    1991-01-01

    Magnetic resonance (MR) images of a total of 195 patients with cervical (125) or thoracic (70) spinal cord injury were reviewed. The imaging studies of the spinal cord lesions were correlated with clinical manifestations. Sequential MR imaging revealed hypointensity on T1-weighted images (T1WI) and hyperintensity on T2-weighted images (T2WI) in all patients, except for five patients showing no signal changes and two showing isointensity, suggesting gliosis, myelomalacia, and syringomyelia. Spinal cord lesions were classified into four types: small lesions, large lesions, complete transverse, and longitudinal rupture. These lesions were well correlated with the severity of injury and paralysis. Complete paralysis was frequently associated with enlarged, complete transverse for cervical spinal cord injury, and longitudinal ruptured or thinned complete transverse for thoracic spinal cord injury. The height of paralysis was well in agreement with that of lesions. For incomplete paralysis, localized lesions were seen within the spinal cord, coinciding with the paralysis or severity. Traumatic syringomyelia was seen in 17 patients (8.7%)-- for the cervical site (10 patients, 8%) and the thoracic site (7 patients, 10%). When homogeneous and marginally clear hypointensity is shown on T1-weighted images and vacuolated hyperintensity is shown on T2-weighted images, in addition to lesions spreading two or more cords or 1.5 or more cords above the nervous root level of paralysis, traumatic syringomyelia is strongly suspected, requiring the follow up observation. (N.K.)

  20. Spatial statistics of magnetic field in two-dimensional chaotic flow in the resistive growth stage

    Energy Technology Data Exchange (ETDEWEB)

    Kolokolov, I.V., E-mail: igor.kolokolov@gmail.com [Landau Institute for Theoretical Physics RAS, 119334, Kosygina 2, Moscow (Russian Federation); NRU Higher School of Economics, 101000, Myasnitskaya 20, Moscow (Russian Federation)

    2017-03-18

    The correlation tensors of magnetic field in a two-dimensional chaotic flow of conducting fluid are studied. It is shown that there is a stage of resistive evolution where the field correlators grow exponentially with time. The two- and four-point field correlation tensors are computed explicitly in this stage in the framework of Batchelor–Kraichnan–Kazantsev model. They demonstrate strong temporal intermittency of the field fluctuations and high level of non-Gaussianity in spatial field distribution.

  1. Staging of cervical carcinoma: accuracy of magnetic resonance imaging and computed tomography.

    Science.gov (United States)

    Janus, C L; Mendelson, D S; Moore, S; Gendal, E S; Dottino, P; Brodman, M

    1989-06-01

    A prospective study was undertaken to assess the ability of magnetic resonance imaging (MRI) to stage cervical carcinoma. Compared to computed tomography (CT), MRI showed a high degree of accuracy in correctly demonstrating involvement of the vagina, parametria and sidewalls, bladder, and lymph nodes but tended to overestimate disease in all of the categories studied. Large-scale studies comparing the two modalities are necessary because the most accurate staging of cervical carcinoma is crucial for selecting the best treatment protocols.

  2. Preliminary results of endorectal surface coil magnetic resonance imaging for local staging of prostate cancer

    NARCIS (Netherlands)

    Jager, G. J.; Barentsz, J. O.; de la Rosette, J. J.; Rosenbusch, G.

    1994-01-01

    To evaluate the effectiveness of endorectal surface coil (ERC) magnetic resonance imaging (MRI) in the local staging of adenocarcinoma of the prostate (ACP). A total of 23 patients who were considered candidates for radical prostatectomy because of clinically localized ACP were examined by ERC-MRI.

  3. [Modulating effect of weak combined magnetic fields on duration of mealworm beetle Tenebrio molitor metamorphosis stage].

    Science.gov (United States)

    Novikov, V V; Sheĭman, I M; Iablokova, E V; Fesenko, E E

    2014-01-01

    It is shown that an exposure of pupae of the mealworm beetle Tenebrio molitor to the combined static (42 μT) and very weak alternating (250 nT) magnetic fields exerts different influence, depending on the frequency of the alternating magnetic field, on duration of metamorphosis processes in these insects. For instance, an exposure of pupae to weak combined magnetic fields, adjusted to the frequency of ion cyclotron resonance for glutaminic acid (4,4 Hz), stimulates metamorphosis process--a transitional stage from pupae to imago lasts shorter. An inhibiting effect was observed when adjusted to the frequency of ion cyclotron resonance for Ca2 (32,2 Hz). At some frequencies this effect is not seen. For instance, an exposure at a frequency of ion cyclotron resonance for K+ (16,5 Hz) exerts no noticeable effect on the duration of the pupal metamorphosis stage.

  4. The progress in diagnostic imaging for staging of bladder and prostate cancer. Endorectal magnetic resonance imaging and magnetization transfer contrast

    Energy Technology Data Exchange (ETDEWEB)

    Arima, Kiminobu; Hayashi, Norio; Yanagawa, Makoto; Kawamura, Juichi; Kobayashi, Shigeki; Takeda, Kan [Mie Univ., Tsu (Japan). School of Medicine; Sugimura, Yoshiki

    1999-08-01

    We retrospectively studied the staging accuracy of endorectal magnetic resonance imaging (MRI) in comparison with transrectal ultrasound examination (TRUS) for 71 localized bladder cancers and 19 localized prostate cancers (PC) radically resected. The accuracy of clinical staging for bladder cancer in endorectal MRI and TRUS was 85.9% and 69.2%, respectively. The presence or absence of the continuity of submucosal enhancement on T2-weighted MRI images could be useful for the staging of bladder cancer. The accuracy of the seminal vesicular invasion for prostate cancer in endorectal MRI and TRUS was 95% and 63%, respectively. To determine whether magnetization transfer contrast (MTC) provides additional information in the diagnosis of prostate cancer, the magnetization transfer ratios (MTRs) were calculated in 22 patients with PC, 5 with benign prostatic hyperplasia (BPH) and 4 controls. The mean MTR in the peripheral zone of the normal prostate (8.0%{+-}3.4 [standard deviation]) showed a statistically significant decrease relative to that in the inner zone of the normal prostate (27.4%{+-}3.4, p<0.01), BPH (25.5%{+-}3.7, p<0.01), pre-treatment PC (30.6%{+-}5.9, p<0.01), and PC after hormonal therapy (20.3%{+-}6.3, p<0.01). The mean MTR in pre-treatment PC was significantly higher than that in BPH, or in PC after hormonal therapy (p<0.01). MTC was considered to be useful for conspicuity of prostate cancer lesion. (author)

  5. Coronal rain in magnetic bipolar weak fields

    Science.gov (United States)

    Xia, C.; Keppens, R.; Fang, X.

    2017-07-01

    Aims: We intend to investigate the underlying physics for the coronal rain phenomenon in a representative bipolar magnetic field, including the formation and the dynamics of coronal rain blobs. Methods: With the MPI-AMRVAC code, we performed three dimensional radiative magnetohydrodynamic (MHD) simulation with strong heating localized on footpoints of magnetic loops after a relaxation to quiet solar atmosphere. Results: Progressive cooling and in-situ condensation starts at the loop top due to radiative thermal instability. The first large-scale condensation on the loop top suffers Rayleigh-Taylor instability and becomes fragmented into smaller blobs. The blobs fall vertically dragging magnetic loops until they reach low-β regions and start to fall along the loops from loop top to loop footpoints. A statistic study of the coronal rain blobs finds that small blobs with masses of less than 1010 g dominate the population. When blobs fall to lower regions along the magnetic loops, they are stretched and develop a non-uniform velocity pattern with an anti-parallel shearing pattern seen to develop along the central axis of the blobs. Synthetic images of simulated coronal rain with Solar Dynamics Observatory Atmospheric Imaging Assembly well resemble real observations presenting dark falling clumps in hot channels and bright rain blobs in a cool channel. We also find density inhomogeneities during a coronal rain "shower", which reflects the observed multi-stranded nature of coronal rain. Movies associated to Figs. 3 and 7 are available at http://www.aanda.org

  6. Validation of Wendelstein 7-X fabrication and assembly stages by magnetic field calculations

    International Nuclear Information System (INIS)

    Andreeva, T.; Kislinger, J.

    2005-01-01

    The Wendelstein 7-X stellarator, which is currently under construction in Greifswald, is a 5-period machine, and many of the planned operational plasma scenarios are characterized by a rotational transform t/2p =1 at the plasma boundary. Such magnetic configurations are very sensitive to the symmetry breaking perturbations caused by fabrication and assembly errors, which can occur at different stages of the device construction. As a consequence, new islands at any periodicity can be produced, existing islands can be modified, stochastic regions can be enhanced and power load onto the divertor plates can be increased. Therefore the high precision of the machine construction is a very important issue, and evaluation of the magnetic field is necessary for the continuous validation of the fabrication and assembly stages with respect to their impact on the magnetic field perturbation. Analysis of the first fabricated winding packs (WPs) has shown that the fabrication errors can be divided into the systematical and statistical parts [1]. The systematic deviations add only negligible field components and don't perturb 5-fold symmetry of the machine, whilst the statistical deviations cause the disturbance of the machine periodicity. For that estimation of the magnetic field perturbation the numerical procedure has been developed [2], which describes statistically the randomly distributed errors, taken within the given tolerances or uses the actual measurements available as an input parameter. Since the construction of the magnet system of W7-X is subdivided into two main phases fabrication of components by industrial contractors and assembly of these components into the magnet system at the Greifswald site, the analysis of the magnetic field perturbation starts from the consideration of the impact of the WPs geometry deviations during the manufacturing stage. (Author)

  7. Dynamics of Magnetized Plasma Jets and Bubbles Launched into a Background Magnetized Plasma

    Science.gov (United States)

    Wallace, B.; Zhang, Y.; Fisher, D. M.; Gilmore, M.

    2016-10-01

    The propagation of dense magnetized plasma, either collimated with mainly azimuthal B-field (jet) or toroidal with closed B-field (bubble), in a background plasma occurs in a number of solar and astrophysical cases. Such cases include coronal mass ejections moving in the background solar wind and extragalactic radio lobes expanding into the extragalactic medium. Understanding the detailed MHD behavior is crucial for correctly modeling these events. In order to further the understanding of such systems, we are investigating the injection of dense magnetized jets and bubbles into a lower density background magnetized plasma using a coaxial plasma gun and a background helicon or cathode plasma. In both jet and bubble cases, the MHD dynamics are found to be very different when launched into background plasma or magnetic field, as compared to vacuum. In the jet case, it is found that the inherent kink instability is stabilized by velocity shear developed due to added magnetic tension from the background field. In the bubble case, rather than directly relaxing to a minimum energy Taylor state (spheromak) as in vacuum, there is an expansion asymmetry and the bubble becomes Rayleigh-Taylor unstable on one side. Recent results will be presented. Work supported by the Army Research Office Award No. W911NF1510480.

  8. Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compression

    Science.gov (United States)

    Varshnay, N. K.; Singh, A.; Benerji, N. S.

    2017-02-01

    Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compression suitable for material processing applications are presented here. The laser incorporates in-built compact gas circulation and gas cooling to ensure fresh gas mixture between the electrodes for repetitive operation. A magnetically coupled tangential blower is used for gas circulation inside the laser chamber for repetitive operation. The exciter consists of C-C energy transfer circuit and thyratron is used as a high-voltage main switch with single-stage magnetic pulse compression (MPC) between thyratron and the laser electrodes. Low inductance of the laser head and uniform and intense pre-ionization are the main features of the electric circuit used in the laser. A 250 ns rise time voltage pulse was compressed to 100 ns duration with a single-stage magnetic pulse compressor using Ni-Zn ferrite cores. The laser can generate about 150 mJ at ˜100 Hz rep-rate reliably from a discharge volume of 100 cm 3. 2D spatial laser beam profile generated is presented here. The profile shows that the laser beam is completely filled with flat-top which is suitable for material processing applications. The SEM image of the microhole generated on copper target is presented here.

  9. The progress in diagnostic imaging for staging of bladder and prostate cancer. Endorectal magnetic resonance imaging and magnetization transfer contrast

    International Nuclear Information System (INIS)

    Arima, Kiminobu; Hayashi, Norio; Yanagawa, Makoto; Kawamura, Juichi; Kobayashi, Shigeki; Takeda, Kan; Sugimura, Yoshiki

    1999-01-01

    We retrospectively studied the staging accuracy of endorectal magnetic resonance imaging (MRI) in comparison with transrectal ultrasound examination (TRUS) for 71 localized bladder cancers and 19 localized prostate cancers (PC) radically resected. The accuracy of clinical staging for bladder cancer in endorectal MRI and TRUS was 85.9% and 69.2%, respectively. The presence or absence of the continuity of submucosal enhancement on T2-weighted MRI images could be useful for the staging of bladder cancer. The accuracy of the seminal vesicular invasion for prostate cancer in endorectal MRI and TRUS was 95% and 63%, respectively. To determine whether magnetization transfer contrast (MTC) provides additional information in the diagnosis of prostate cancer, the magnetization transfer ratios (MTRs) were calculated in 22 patients with PC, 5 with benign prostatic hyperplasia (BPH) and 4 controls. The mean MTR in the peripheral zone of the normal prostate (8.0%±3.4 [standard deviation]) showed a statistically significant decrease relative to that in the inner zone of the normal prostate (27.4%±3.4, p<0.01), BPH (25.5%±3.7, p<0.01), pre-treatment PC (30.6%±5.9, p<0.01), and PC after hormonal therapy (20.3%±6.3, p<0.01). The mean MTR in pre-treatment PC was significantly higher than that in BPH, or in PC after hormonal therapy (p<0.01). MTC was considered to be useful for conspicuity of prostate cancer lesion. (author)

  10. Differential diagnosis and staging of urological tumors by magnetic resonance imaging compared with computed tomography

    International Nuclear Information System (INIS)

    Nishimura, Kazuo; Okada, Yusaku; Takeuchi, Hideo; Miyakawa, Mieko; Okada, Kenichiro; Yoshida, Osamu; Nishimura, Kazumasa

    1987-01-01

    Magnetic resonance imaging (MRI) was performed on 49 urological tumors (11 renal cell carcinomas, 3 renal pelvic cancers, 2 renal angiomyolipomas, 1 renal leiomyosarcoma, 1 large renal cvst, 4 adrenal tumors, 11 bladder cancers, 2 bone metastasis from bladder cancer, 10 prostatic cancers, 1 prostatic sarcoma, 1 urethral cancer, 1 penile cancer and 1 perivesical granuloma) since October 1985 to September 1986. MRI was performed using a Signa (G.E.) with a 1.5 T superconductive magnet and 3 images, including T1 weighted image, T2 weighted image, and proton density image, were obtained. In conclusion MRI is a noninvasive examination and gives more information than computed tomography despite its high cost. In renal cell carcinoma, the chemical shift in MRI and clear visualization of tumor thrombus enable accurate staging. Differential diagnosis from other renal mass lesions may be possible by the T2 weighted image. In adrenal disease, most of the adrenal masses can be differentiated, but in some cases it is impossible. In bladder cancer, wall invasion of tumor may be evaluated in T2 weighted image, and MRI is suitable for staging of locally advanced tumor. In prostatic cancer, visualization of periprostatic plexus and differentiation between internal and external gland may enable local staging and identification of low stage tumors. (author)

  11. Structural and magnetic changes in MgO-based magnetic tunneling junctions during the early stages of annealing

    Science.gov (United States)

    Anderson, G. I. R.; Wei, H.-X.; Porter, N. A.; Arena, D. A.; Dvorak, J.; Han, X.-F.; Marrows, C. H.

    2010-03-01

    We have studied the effects of the initial stages of the annealing on magnetic tunnel junctions with MgO barriers and CoFeB electrodes. We report changes in the resistance-voltage characteristics and tunneling magnetoresistance for patterned transport junctions, and correlate these with the observed changes in the structural and magnetic interface morphologies determined by soft X-ray resonant magnetic scattering from sheet films from the same wafer. An important feature of our experiment was that all measurements were carried out within the soft X-ray diffractometer on samples from the same wafer subjected to simultaneous annealing cycles, so that our magnetotransport and scattering data are directly comparable. The as-grown junction showed a tunneling magnetoresistance ratio of 5.5%, and a specific barrier resistance of 85.6 kΩ μm2. A 200C anneal for 1 h resulted in a small rise in barrier resistance and magnetoresistance coupled with a smoothing of the magnetic interfaces, consistent with the healing of barrier defects and removal of tunneling hot-spots. A subsequent 300C anneal for a further hour resulted in further smoothing, and a rise in the magnetoresistance ratio to 72%, and a much weaker dependence of the parallel state resistance upon voltage bias, indicating the development of (0 0 1) crystallographic texture in the electrodes. Annealing to 325C yielded a further decrease in magnetic interface width (the quadrature sum of roughness and intermixing length scales). The reduction in interface width for Co species occurred at higher temperatures than for Fe throughout the experiments.

  12. Structural and magnetic changes in MgO-based magnetic tunneling junctions during the early stages of annealing

    International Nuclear Information System (INIS)

    Anderson, G.I.R.; Wei, H.-X.; Porter, N.A.; Arena, D.A.; Dvorak, J.; Han, X.-F.; Marrows, C.H.

    2010-01-01

    We have studied the effects of the initial stages of the annealing on magnetic tunnel junctions with MgO barriers and CoFeB electrodes. We report changes in the resistance-voltage characteristics and tunneling magnetoresistance for patterned transport junctions, and correlate these with the observed changes in the structural and magnetic interface morphologies determined by soft X-ray resonant magnetic scattering from sheet films from the same wafer. An important feature of our experiment was that all measurements were carried out within the soft X-ray diffractometer on samples from the same wafer subjected to simultaneous annealing cycles, so that our magnetotransport and scattering data are directly comparable. The as-grown junction showed a tunneling magnetoresistance ratio of 5.5%, and a specific barrier resistance of 85.6kΩμm 2 . A 200 deg. C anneal for 1 h resulted in a small rise in barrier resistance and magnetoresistance coupled with a smoothing of the magnetic interfaces, consistent with the healing of barrier defects and removal of tunneling hot-spots. A subsequent 300 deg. C anneal for a further hour resulted in further smoothing, and a rise in the magnetoresistance ratio to 72%, and a much weaker dependence of the parallel state resistance upon voltage bias, indicating the development of (001) crystallographic texture in the electrodes. Annealing to 325 deg. C yielded a further decrease in magnetic interface width (the quadrature sum of roughness and intermixing length scales). The reduction in interface width for Co species occurred at higher temperatures than for Fe throughout the experiments.

  13. First stage of INTRAMAP: INtegrated Transantarctic Mountains and Ross Sea Area Magnetic Anomaly Project

    Directory of Open Access Journals (Sweden)

    D. Damaske

    1999-06-01

    Full Text Available INTRAMAP (INtegrated Transantarctic Mountains and Ross Sea Area Magnetic Anomaly Project is an international effort to merge the magnetic data acquired throughout the "Ross Sea Antarctic Sector" (south of 60°S between 135°-255°E including the Transantarctic Mountains (TAM, the Ross Sea, Marie Byrd Land, and the Pacific coast, and also to begin the compilation efforts for new data over the Wilkes Basin. This project is a component of the continental scale Antarctic Digital Magnetic Anomaly Project (ADMAP. The first stage of INTRAMAP addresses the analysis and merging of GITARA (1991-1994 and GANOVEX (1984 aeromagnetic surveys together with ground magnetic data (1984-1989. The combined data sets cover an area of approximately 30 km2 over Victoria Land and adjacent Ross Sea. Map and profile gridding were implemented to integrate the data sets. These approaches are studied for improving existing strategies to adopt for the whole magnetic compilation effort. The final microlevelled grid that we produce is a new tool for regional interpretation of the main tectonic and geologic features of this sector of Antarctica.

  14. A versatile rotary-stage high frequency probe station for studying magnetic films and devices

    Energy Technology Data Exchange (ETDEWEB)

    He, Shikun [Data Storage Institute, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, #08-01, Innovis 138634 (Singapore); Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore); Meng, Zhaoliang; Huang, Lisen; Yap, Lee Koon; Zhou, Tiejun [Data Storage Institute, A*STAR (Agency for Science, Technology and Research), 2 Fusionopolis Way, #08-01, Innovis 138634 (Singapore); Panagopoulos, Christos [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore)

    2016-07-15

    We present a rotary-stage microwave probe station suitable for magnetic films and spintronic devices. Two stages, one for field rotation from parallel to perpendicular to the sample plane (out-of-plane) and the other intended for field rotation within the sample plane (in-plane) have been designed. The sample probes and micro-positioners are rotated simultaneously with the stages, which allows the field orientation to cover θ from 0{sup ∘} to 90{sup ∘} and φ from 0{sup ∘} to 360{sup ∘}. θ and φ being the angle between the direction of current flow and field in a out-of-plane and an in-plane rotation, respectively. The operation frequency is up to 40 GHz and the magnetic field up to 1 T. The sample holder vision system and probe assembly are compactly designed for the probes to land on a wafer with diameter up to 3 cm. Using homemade multi-pin probes and commercially available high frequency probes, several applications including 4-probe DC measurements, the determination of domain wall velocity, and spin transfer torque ferromagnetic resonance are demonstrated.

  15. 3-D MHD modeling and stability analysis of jet and spheromak plasmas launched into a magnetized plasma

    Science.gov (United States)

    Fisher, Dustin; Zhang, Yue; Wallace, Ben; Gilmore, Mark; Manchester, Ward; Arge, C. Nick

    2016-10-01

    The Plasma Bubble Expansion Experiment (PBEX) at the University of New Mexico uses a coaxial plasma gun to launch jet and spheromak magnetic plasma configurations into the Helicon-Cathode (HelCat) plasma device. Plasma structures launched from the gun drag frozen-in magnetic flux into the background magnetic field of the chamber providing a rich set of dynamics to study magnetic turbulence, force-free magnetic spheromaks, and shocks. Preliminary modeling is presented using the highly-developed 3-D, MHD, BATS-R-US code developed at the University of Michigan. BATS-R-US employs an adaptive mesh refinement grid that enables the capture and resolution of shock structures and current sheets, and is particularly suited to model the parameter regime under investigation. CCD images and magnetic field data from the experiment suggest the stabilization of an m =1 kink mode trailing a plasma jet launched into a background magnetic field. Results from a linear stability code investigating the effect of shear-flow as a cause of this stabilization from magnetic tension forces on the jet will be presented. Initial analyses of a possible magnetic Rayleigh Taylor instability seen at the interface between launched spheromaks and their entraining background magnetic field will also be presented. Work supported by the Army Research Office Award No. W911NF1510480.

  16. Imaging vascular function for early stage clinical trials using dynamic contrast-enhanced magnetic resonance imaging

    Energy Technology Data Exchange (ETDEWEB)

    Leach, M.O.; Orton, M. [Institute of Cancer Research and Royal Marsden NHS Foundation Trust, Cancer Research UK and EPSRC Cancer Imaging Centre, Sutton, Surrey (United Kingdom); Morgan, B. [Univ. of Leicester, College of Medicine, Biological Sciences and Psychology, Leicester (United Kingdom); Tofts, P.S. [Brighton and Sussex Medical School, Univ. of Sussex, Clinical Imaging Sciences Centre, Sussex (United Kingdom); Buckley, D.L. [University of Leeds, Division of Medical Physics, Leeds (United Kingdom); Huang, W. [Oregon Health and Science Univ., Advanced Imaging Research Centre, Portland, OR (United States); Horsfield, M.A. [Medical Physics Section, Leicester Royal Infirmary, Dept. of Cardiovascular Sciences, Leicester (United Kingdom); Chenevert, T.L. [Univ. of Michigan Health System, Ann Arbor, MI (United States); Collins, D.J. [Royal Marsden Hospital NHS Foundation Trust, Cancer Research UK and EPSRC Cancer Imaging Centre, Sutton, Surrey (United Kingdom); Jackson, A. [Univ. of Manchester, Wolfson Molecular Imaging Centre, Withington, Manchester, M20 3LJ (United Kingdom); Lomas, D. [Univ. of Cambridge, Dept. of Radiology, Cambridge (United Kingdom); Whitcher, B. [Unit 2 Greenways Business Park, Mango Solutions, Chippenham (United Kingdom); Clarke, L. [Cancer Imaging Program, Imaging Technology Development Branch, Rockville, MD (United States); Plummer, R. [Univ. of Newcastle Upon Tyne, The Medical School, Medical Oncology, Northern Inst. for Cancer Research, Newcastle Upon Tyne (United Kingdom); Judson, I. [Royal Marsden Hospital, Sutton, Surrey (United Kingdom); Jones, R. [Beatson West of Scotland Cancer Centre, Glasgow (United Kingdom); Alonzi, R. [Mount Vernon Cancer Centre, Northwood (United Kingdom); Brunner, T. [Gray Inst. for Radiation, Oncology and Biology, Oxford (United Kingdom); Koh, D.M. [Royal Marsden NHS Foundation Trust, Diagnostic Radiology, Sutton, Surrey (United Kingdom)] [and others

    2012-07-15

    Many therapeutic approaches to cancer affect the tumour vasculature, either indirectly or as a direct target. Dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) has become an important means of investigating this action, both pre-clinically and in early stage clinical trials. For such trials, it is essential that the measurement process (i.e. image acquisition and analysis) can be performed effectively and with consistency among contributing centres. As the technique continues to develop in order to provide potential improvements in sensitivity and physiological relevance, there is considerable scope for between-centre variation in techniques. A workshop was convened by the Imaging Committee of the Experimental Cancer Medicine Centres (ECMC) to review the current status of DCE-MRI and to provide recommendations on how the technique can best be used for early stage trials. This review and the consequent recommendations are summarised here. (orig.)

  17. Gadolinium-enhanced dynamic magnetic resonance imaging with endorectal coil for local staging of rectal cancer

    International Nuclear Information System (INIS)

    Tamakawa, Mitsuharu; Kawaai, Yuriko; Shirase, Ryuji

    2010-01-01

    The aim of this study was to evaluate the accuracy of dynamic gadolinium (Gd)-enhanced magnetic resonance imaging (MRI) with endorectal coil for assessing tumor invasion based on simple classification criteria. A total of 58 patients with operable primary rectal cancer underwent preoperative MRI. An enhancement pattern in Gd-enhanced dynamic MRI with regard to tumor penetration was clarified. Retrospectively, two observers independently scored T2-weighted MRI and T2-weighted MRI combined with Gd-enhanced dynamic MRI for tumor penetration using the following criteria: With Gd-enhanced dynamic MRI, T1 tumors showed an early enhanced line around the tumor as rim enhancement; T2 tumors appeared as black lines or double layers, as the muscularis propria kept its integrity; T3 tumors showed partial discontinuity of the muscularis propria as a dotted line and a perforated area as an interrupted line. A confidence level scoring system was used, and receiver operating characteristic curves were generated. There were no significant differences at the T1 stage. There were significant differences for observer 1 (P=0.001 for observer 1) at the T2 stage. There were significant differences for both observers (P=0.001 for observer 1 and P=0.005 for observer 2) at the T3 stage. Our criteria for Gd-enhanced dynamic MRI were effective for T3 stage tumors. (author)

  18. Observations and modeling of magnetized plasma jets and bubbles launched into a transverse B-field

    Science.gov (United States)

    Fisher, Dustin M.; Zhang, Yue; Wallace, Ben; Gilmore, Mark; Manchester, Ward B., IV; van der Holst, Bart; Rogers, Barrett N.; Hsu, Scott C.

    2017-10-01

    Hot, dense, plasma structures launched from a coaxial plasma gun on the HelCat dual-source plasma device at the University of New Mexico drag frozen-in magnetic flux into the chamber's background magnetic field providing a rich set of dynamics to study magnetic turbulence, force-free magnetic spheromaks, shocks, as well as CME-like dynamics possibly relevant to the solar corona. Vector magnetic field data from an eleven-tipped B-dot rake probe and images from an ultra-fast camera will be presented in comparison with ongoing MHD modeling using the 3-D MHD BATS-R-US code developed at the University of Michigan. BATS-R-US employs an adaptive mesh refinement grid (AMR) that enables the capture and resolution of shock structures and current sheets and is uniquely suited for flux-rope expansion modeling. Recent experiments show a possible magnetic Rayleigh-Taylor (MRT) instability that appears asymmetrically at the interface between launched spheromaks (bubbles) and their entraining background magnetic field. Efforts to understand this instability using in situ measurements, new chamber boundary conditions, and ultra-fast camera data will be presented. Work supported by the Army Research Office Award No. W911NF1510480.

  19. Pancreatic neuroendocrine neoplasms: Magnetic resonance imaging features according to grade and stage

    Science.gov (United States)

    De Robertis, Riccardo; Cingarlini, Sara; Tinazzi Martini, Paolo; Ortolani, Silvia; Butturini, Giovanni; Landoni, Luca; Regi, Paolo; Girelli, Roberto; Capelli, Paola; Gobbo, Stefano; Tortora, Giampaolo; Scarpa, Aldo; Pederzoli, Paolo; D’Onofrio, Mirko

    2017-01-01

    AIM To describe magnetic resonance (MR) imaging features of pancreatic neuroendocrine neoplasms (PanNENs) according to their grade and tumor-nodes-metastases stage by comparing them to histopathology and to determine the accuracy of MR imaging features in predicting their biological behavior. METHODS This study was approved by our institutional review board; requirement for informed patient consent was waived due to the retrospective nature of the study. Preoperative MR examinations of 55 PanNEN patients (29 men, 26 women; mean age of 57.6 years, range 21-83 years) performed between June 2013 and December 2015 were reviewed. Qualitative and quantitative features were compared between tumor grades and stages determined by histopathological analysis. RESULTS Ill defined margins were more common in G2-3 and stage III-IV PanNENs than in G1 and low-stage tumors (P < 0.001); this feature had high specificity in the identification of G2-3 and stage III-IV tumors (90.3% and 96%, 95%CI: 73.1-97.5 and 77.7-99.8). The mean apparent diffusion coefficient value was significantly lower in G2-3 and stage III-IV lesions compared to well differentiated and low-stage tumors (1.09 × 10-3 mm2/s vs 1.45 × 10-3 mm2/s and 1.10 × 10-3 mm2/s vs 1.53 × 10-3 mm2/s, P = 0.003 and 0.001). Receiving operator characteristic analysis determined optimal cut-offs of 1.21 and 1.28 × 10-3 mm2/s for the identification of G2-3 and stage III-IV tumors, with sensitivity and specificity values of 70.8/80.7% and 64.5/64% (95%CI: 48.7-86.6/60-92.7 and 45.4-80.2/42.6-81.3). CONCLUSION MR features of PanNENs vary according to their grade of differentiation and their stage at diagnosis and could predict the biological behavior of these tumors. PMID:28127201

  20. Operational studies and expected performance of superconducting quadrupole magnets in the first stages of secondary beams

    International Nuclear Information System (INIS)

    Garbincius, P.H.; Mazur, P.O.; Stanek, R.P.

    1983-08-01

    A low current, large bore, epoxy impregnated superconducting quadrupole magnet was constructed at Argonne National Laboratory as a possible prototype for secondary beam use. The quadrupole magnet was placed in the Fermilab P-West High Intensity Area beam for beam quenching tests. Tests were performed by targetting a primary proton beam directly onto the quadrupole coil and by using the quadrupole in its anticipated role as part of the first stage flux collection triplet for a zero degree anti-proton secondary beam formed from the decays of neutral Lambda particles. Comparing the results with similar tests performed using forced flow Energy Saver dipoles shows that the epoxy impregnated quadrupoles have a much greater sensitivity to beam induced quenching at a similar fraction of the conductor short sample limit. Using the CASIM program, calculations indicate that such eopxy impregnated coils would not be viable as first stage flux collection elements without appreciable collimation and subsequent loss of secondary beam acceptance. Quadrupoles based on Energy Saver technology appear capable of tolerating acceptable primary beam intensities. The momentum dispersing bends will require even larger aperture superconducting dipoles or neutral beam dump within the bend string

  1. Magnetic resonance arthrographic findings of presumed stage-2 adhesive capsulitis: focus on combined rotator cuff pathology.

    Science.gov (United States)

    Yoo, Jae Chul; Ahn, Jin Hwan; Lee, Yong Seuk; Koh, Kyoung Hwan

    2009-01-01

    The purpose of this study was to report the magnetic resonance arthrography (MRA) findings of patients considered to have stage-2 idiopathic adhesive capsulitis and to identify differences in rotator cuff pathologies between 2 age groups (ie, =or60 years). Eighty-one patients, considered to have stage-2 idiopathic adhesive capsulitis based on medical history and a physical examination underwent MRA. Magnetic resonance evaluations focused on combined pathologies other than adhesive capsulitis, especially on the supraspinatus tendon. The pathologies of supraspinatus tendon were divided into 4 categories: normal, tendinosis, partial-tears, and full-thickness tears. Mean patient age was 66 years and mean symptom duration was 8.9 months. There were 38 men and 43 women. Overall, 50 patients (61.7%) showed some form of supraspinatus tendon pathology [small full-thickness tears 6 (7.4%), partial-thickness tears 25 (30.9%), and supraspinatus tendon tendinosis 19 (23.5%)]. The most common MRA finding, other than rotator cuff pathology, was the impression of adhesive capsulitis in 58 patients (71.6%). Group 2 (>60 years) showed a higher prevalence of full and partial-thickness tears (Padhesive capsulitis patients showed some form of supraspinatus tendon tear by MRA, and adhesive capsulitis had a full-thickness tear. Adhesive capsulitis patients older than 60 years appeared to be more likely to have a supraspinatus tendon tear.

  2. Accretion on to Magnetic White Dwarfs

    Directory of Open Access Journals (Sweden)

    Wickramasinghe Dayal

    2014-01-01

    The polars have no counterparts in neutron star systems and their study provides unique insights into the complex nature of the magnetospheric boundary. The observed properties of accretion shocks at the white dwarf surface such as the anomalous soft-X-ray excess and its time variability provide strong support for the hypothesis that under certain circumstances the field channelled funnel flow is “blobby”. This has been attributed to interchange instabilities such as the Magnetic Rayleigh-Taylor instability in the shocked gas at the stream-magnetosphere boundary where the stream fragments into discrete clumps of gas. As the clumps penetrate into the magnetosphere, they are shredded into smaller mass blobs via the Kelvin-Helmholtz instability that then couple on to field lines over an extended inner transition region in the orbital plane. The more massive blobs penetrate deep into the photosphere of the white dwarf releasing their energy as a reprocessed soft-X-ray black body component. Although similar instabilities are expected in the inner transition region in disced accretion albeit on a different scale there has been no direct observational evidence for blobby accretion in the generally lower field and disced IPs.

  3. Magnetic anvil cells driven by pulsed-power generators

    Science.gov (United States)

    Gourdain, P.-A.; Adams, M. B.; Evans, M.; McBride, R. D.; Sefkow, A. B.; Seyler, C. E.; Collins, G.

    2017-10-01

    Magnetic anvil cells (MAC) use a gas, foam or solid damper to compress a material sample via magnetic pinch forces. Unlike diamond anvil cells (DAC), which are limited by the material strength of diamond, MAC have no mechanical limits. Only the amount of current that can be delivered to the MAC limits the final pressure at which a material sample can be compressed. Another main advantage of MAC over DAC is the ability to heat the sample, allowing to produce warm dense matter. The damper that surrounds the material sample has several functions. Initially, it diverts the current away from the sample, preventing electrothermal instabilities inside the sample. When the damper has fully imploded, the current commutes from the damper to the sample in less than 10 ns. Since the current is already on its way to reach a maximum, hundreds of kilobars are suddenly applied to the sample, limiting plasma ablation and surface inhomogeneity, which can later seed magnetic Rayleigh-Taylor instabilities. This work shows that the phase and chemical composition of the damper is critical to the homogeneity of the compressed sample and will change depending on the current level required to reach the final pressure. This research is partially supported by the DOE Grant Number DE-SC0016252.

  4. Preoperative Magnetic Resonance Imaging in Patients With Stage I Invasive Ductal Breast Cancer: A Prospective Randomized Study.

    Science.gov (United States)

    Brück, N; Koskivuo, I; Boström, P; Saunavaara, J; Aaltonen, R; Parkkola, R

    2018-03-01

    Preoperative magnetic resonance imaging has become an important complementary imaging technique in patients with breast cancer, providing additional information for preoperative local staging. Magnetic resonance imaging is recommended selectively in lobular breast cancer and in patients with dense breast tissue in the case when mammography and ultrasound fail to fully evaluate the lesion, but the routine use of magnetic resonance imaging in all patients with invasive ductal carcinoma is controversial. The purpose of this randomized study was to investigate the diagnostic value of preoperative magnetic resonance imaging and its impact on short-term surgical outcome in newly diagnosed unifocal stage I invasive ductal carcinoma. A total of 100 patients were randomized to either receive preoperative breast magnetic resonance imaging or to be scheduled directly to operation without magnetic resonance imaging on a 1:1 basis. There were 50 patients in both study arms. In 14 patients (28%), breast magnetic resonance imaging detected an additional finding and seven of them were found to be malignant. Six additional cancer foci were found in the ipsilateral breast and one in the contralateral breast. Magnetic resonance imaging findings caused a change in planned surgical management in 10 patients (20%). Mastectomy was performed in six patients (12%) in the magnetic resonance imaging group and in two patients (4%) in the control group ( p = 0.140). The breast reoperation rate was 14% in the magnetic resonance imaging group and 24% in the control group ( p = 0.202). The mean interval between referral and first surgical procedure was 34 days in the magnetic resonance imaging group and 21 days in the control group ( p magnetic resonance imaging may be beneficial for some patients with early-stage invasive ductal carcinoma, but its routine use is not recommended without specific indications.

  5. Experimental investigation of coaxial-gun-formed plasmas injected into a background transverse magnetic field or plasma

    Science.gov (United States)

    Zhang, Yue; Fisher, Dustin M.; Gilmore, Mark; Hsu, Scott C.; Lynn, Alan G.

    2018-05-01

    Injection of coaxial-gun-formed magnetized plasmas into a background transverse vacuum magnetic field or into a background magnetized plasma has been studied in the helicon-cathode (HelCat) linear plasma device at the University of New Mexico [M. Gilmore et al., J. Plasma Phys. 81, 345810104 (2015)]. A magnetized plasma jet launched into a background transverse magnetic field shows emergent kink stabilization of the jet due to the formation of a sheared flow in the jet above the kink stabilization threshold 0.1kVA [Y. Zhang et al., Phys. Plasmas 24, 110702 (2017)]. Injection of a spheromak-like plasma into a transverse background magnetic field led to the observation of finger-like structures on the side with a stronger magnetic field null between the spheromak and the background field. The finger-like structures are consistent with magneto-Rayleigh-Taylor instability. Jets or spheromaks launched into a background, low-β magnetized plasma show similar behavior as above, respectively, in both cases.

  6. Magnetic resonance imaging of the active second stage of labour: Proof of principle

    International Nuclear Information System (INIS)

    Guettler, F.V.; Heinrich, A.; Rump, J.; Bucourt, M. de; Hamm, B.; Teichgraeber, U.K.; Schnackenburg, B.; Bamberg, C.

    2012-01-01

    To prove that magnetic resonance imaging of foetal anatomy during the active second stage of vaginal delivery is feasible. Initially, five pregnant volunteers around the 30th week of gestation were examined in an open MRI. Based on the findings, one vaginal delivery was acquired under real-time imaging. To monitor the birth status during image acquisition, an MR-compatible wireless cardiotocography (CTG) system was built. Single-shot sequence parameters were optimised to compensate motion artefacts during labour. Safety requirements to monitor the birth process under real-time MR imaging were met. High-resolution MR images were acquired immediately before and after delivery. In one patient, TSE single-shot cinematic sequences of the active second stage of labour were obtained. All sequences were adapted to tolerate movement of the mother and infant, as well as residual noise from the CTG. Furthermore, the MR imaging during labour showed only minor image artefacts. CTG-monitored acquisition of MRI series during the active second stage of delivery is feasible. Image quality should allow various further studies to improve models for birth simulation as well as potential investigation of obstructed labour and obstetric complications. (orig.)

  7. Edge-driven Rayleigh Taylor Instabilities at Transtensional Continental Margins: Western North Island, New Zealand

    Science.gov (United States)

    Stern, T. A.; Houseman, G. A.; Evans, L.

    2011-12-01

    At a continental transform system with an element of extension, regular and thinned lithosphere are juxtaposed. Such a system will be gravitationally unstable as negative buoyancy is created by the regular mantle lithosphere terminating at an abrubt edge with less dense asthenospheric mantle. Finite element experiments with dimensionless ratios of viscosity and density show that such a gravitational instability can grow, migrate and eventually drip off into the lower density asthenosphere providing two criteria are met: lithospheric thinning across the edge is at least 30% or more; and that viscosity at the top of the mantle lithosphere is no more than 2.4 or 4.5 x1021 Pa s, for lithospheric thicknesses of 100 and 200 km respectively. These are low values for regular mantle lithosphere, but are in keeping with mantle lithosphere found adjacent to plate boundaries, or paleo subduction zones. As the mantle lithosphere deforms and migrates away from an edge it both thins and thickens different portions of the overlying crust. At the surface regions of subsidence and uplift migrated in concert with the subjacent gravitational instability. A dimensionless variable analysis of instability development shows that 3 critical dimensionless ratios control the shape, migration speed and form of the instability: η' = ratio of viscosity between crust and mantle; m' = ratio of crust to lithosphere thickness; and d' = portion of mantle lithosphere thinning to initiate the instability. Western North Island, New Zealand, displays characteristics of uplift and subsidence in the past 10-12 Ma, which can be explained by a migrating instability that initiated from the Auckland-Hauraki area around 10 Ma. Transtensional faults developed in mid-North Island from 5 Ma as back-arc spreading from the oceanic Lau Havre trough penetrated into the continental lithosphere of New Zealand. It is this transtensional phase that we argue started the edge-driven instability. The present position of the proposed migrating instability is now beneath the east-west line joining the active volcanoes of Mts Taranaki and Ruapehu. Here seismic, gravity, MT and seismicity evidence show a major, near vertical step in both the Moho and mantle lithosphere. A stacked receiver function profile shows a 7-10 km step in the Moho, and to the north of the step low upper-mantle P and S wave velocities suggests the mantle lithosphere is either very thin or missing. A migrating edge-instability provides a credible explanation for much of the phenomena observed in western North Island providing the mantle lithosphere is of the order of 5 x 1020 Pa s. We propose additional geophysical tests to check on the present position of the instability and to also extend the numerical experiments into three dimensions.

  8. Ablative Rayleigh Taylor instability in the limit of an infinitely large density ratio

    Science.gov (United States)

    Clavin, Paul; Almarcha, Christophe

    2005-05-01

    The instability of ablation fronts strongly accelerated toward the dense medium under the conditions of inertial confinement fusion (ICF) is addressed in the limit of an infinitely large density ratio. The analysis serves to demonstrate that the flow is irrotational to first order, reducing the nonlinear analysis to solve a two-potential flows problem. Vorticity appears at the following orders in the perturbation analysis. This result simplifies greatly the analysis. The possibility for using boundary integral methods opens new perspectives in the nonlinear theory of the ablative RT instability in ICF. A few examples are given at the end of the Note. To cite this article: P. Clavin, C. Almarcha, C. R. Mecanique 333 (2005).

  9. Forensic age estimation based on development of third molars: a staging technique for magnetic resonance imaging.

    Science.gov (United States)

    De Tobel, J; Phlypo, I; Fieuws, S; Politis, C; Verstraete, K L; Thevissen, P W

    2017-12-01

    The development of third molars can be evaluated with medical imaging to estimate age in subadults. The appearance of third molars on magnetic resonance imaging (MRI) differs greatly from that on radiographs. Therefore a specific staging technique is necessary to classify third molar development on MRI and to apply it for age estimation. To develop a specific staging technique to register third molar development on MRI and to evaluate its performance for age estimation in subadults. Using 3T MRI in three planes, all third molars were evaluated in 309 healthy Caucasian participants from 14 to 26 years old. According to the appearance of the developing third molars on MRI, descriptive criteria and schematic representations were established to define a specific staging technique. Two observers, with different levels of experience, staged all third molars independently with the developed technique. Intra- and inter-observer agreement were calculated. The data were imported in a Bayesian model for age estimation as described by Fieuws et al. (2016). This approach adequately handles correlation between age indicators and missing age indicators. It was used to calculate a point estimate and a prediction interval of the estimated age. Observed age minus predicted age was calculated, reflecting the error of the estimate. One-hundred and sixty-six third molars were agenetic. Five percent (51/1096) of upper third molars and 7% (70/1044) of lower third molars were not assessable. Kappa for inter-observer agreement ranged from 0.76 to 0.80. For intra-observer agreement kappa ranged from 0.80 to 0.89. However, two stage differences between observers or between staging sessions occurred in up to 2.2% (20/899) of assessments, probably due to a learning effect. Using the Bayesian model for age estimation, a mean absolute error of 2.0 years in females and 1.7 years in males was obtained. Root mean squared error equalled 2.38 years and 2.06 years respectively. The performance to

  10. Modeling the fine fragmentation following the triggering stage of a vapor explosion

    International Nuclear Information System (INIS)

    Darbord, I.

    1997-01-01

    In the frame of PWR severe accidents, where the core melt, this thesis studies one of the stages of an FCI (fuel coolant interaction) or vapor explosion. An FCI is a rapid evaporation of a coolant when it comes into contact with a hot liquid. More precisely, the subject of this study is the triggering stage of the FCI, when a fuel drop of diameter around one centimeter breaks up into many fragments, diameter of which is around a hundred micrometers. The model describes the cyclic collapse and growth of a vapor bubble around the fuel droplet and its fragmentation. The main features of the model are: - the destabilization of the film or the vapor bubble due to the growth of Rayleigh-Taylor instabilities (those form coolant jets that contact the fuel surface); - The mechanisms of fragmentation, following the contacts (in the case of entrapment of a certain amount of coolant in the fuel, the entrapped coolant evaporates violently after it has been heated to the homogeneous nucleation temperature); - the transient heat transfer from the fragments to the coolant and the elevated vapor production, which leads to an important expansion of the bubble (about this point, the cooling of the fragments has been described by a transient heat transfer coefficient linked to nucleate boiling). The results of the model show good agreement with experimental data. (Author)

  11. Magnetic resonance imaging of the initial active stage of equine laminitis at 4.7 T.

    Science.gov (United States)

    Arble, Jason B; Mattoon, John S; Drost, Wm Tod; Weisbrode, Steven E; Wassenaar, Peter A; Pan, Xueliang; Hunt, Robert J; Belknap, James K

    2009-01-01

    Equine laminitis is a severely debilitating disease. There is a poor understanding of the underlying pathophysiology, and traditional imaging modalities have limited diagnostic capacity. High field strength magnetic resonance (MR) imaging allows direct visualization of the laminae, which other modalities do not. This would prove useful both in assessment of clinical patients and in further investigation into the pathophysiology of the disease. The objective of this study was to characterize the anatomic changes within the equine foot associated with the initial active stage of laminitis. Images obtained using a 4.7 T magnet were compared with digital radiographs using histologic diagnosis as the reference standard. Objective measurements and subjective evaluation for both modalities were evaluated for the ability to predict the histologic diagnosis in horses with clinical signs of laminitis as well as in clinically normal horses and horses that were in a population at risk for developing laminitis. Signal intensity and architectural changes within the corium and laminae were readily seen at 4.7 T, and there was a strong association with the histologic diagnosis of active laminitis. Measurements obtained with MR imaging were more sensitive and specific predictors of laminitis than those obtained radiographically. Subjective evaluation with MR imaging was more sensitive than with radiography and should become more specific with greater understanding of normal anatomy.

  12. Stagnation morphology in Magnetized Liner Inertial Fusion experiments

    Science.gov (United States)

    Gomez, M. R.; Harding, E. C.; Ampleford, D. J.; Jennings, C. A.; Awe, T. J.; Chandler, G. A.; Glinsky, M. E.; Hahn, K. D.; Hansen, S. B.; Jones, B.; Knapp, P. F.; Martin, M. R.; Peterson, K. J.; Rochau, G. A.; Ruiz, C. L.; Schmit, P. F.; Sinars, D. B.; Slutz, S. A.; Weis, M. R.; Yu, E. P.

    2017-10-01

    In Magnetized Liner Inertial Fusion (MagLIF) experiments on the Z facility, an axial current of 15-20 MA is driven through a thick metal cylinder containing axially-magnetized, laser-heated deuterium fuel. The cylinder implodes, further heating the fuel and amplifying the axial B-field. Instabilities, such as magneto-Rayleigh-Taylor, develop on the exterior of the liner and may feed through to the inner surface during the implosion. Monochromatic x-ray emission at stagnation shows the stagnation column is quasi-helical with axial variations in intensity. Recent experiments demonstrated that the stagnation emission structure changed with modifications to the target wall thickness. Additionally, applying a thick dielectric coating to the exterior of the target modified the stagnation column. A new version of the x-ray self-emission diagnostic has been developed to investigate stagnation with higher resolution. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

  13. Single-Stage Step up/down Driver for Permanent-Magnet Synchronous Machines

    Science.gov (United States)

    Chen, T. R.; Juan, Y. L.; Huang, C. Y.; Kuo, C. T.

    2017-11-01

    The two-stage circuit composed of a step up/down dc converter and a three-phase voltage source inverter is usually adopted as the electric vehicle’s motor driver. The conventional topology is more complicated. Additional power loss resulted from twice power conversion would also cause lower efficiency. A single-stage step up/down Permanent-Magnet Synchronous Motor driver for Brushless DC (BLDC) Motor is proposed in this study. The number components and circuit complexity are reduced. The low frequency six-step square-wave control is used to reduce the switching losses. In the proposed topology, only one active switch is gated with a high frequency PWM signal for adjusting the rotation speed. The rotor position signals are fed back to calculate the motor speed for digital close-loop control in a MCU. A 600W prototype circuit is constructed to drive a BLDC motor with rated speed 3000 rpm, and can control the speed of six sections.

  14. Tumour extent and T stage of nasopharyngeal carcinoma: a comparison of magnetic resonance imaging and computed tomographic findings

    Energy Technology Data Exchange (ETDEWEB)

    Poon, P.Y. [deceased, Univ. of British Columbia, Dept. of Diagnostic Imaging, Vancouver, BC (Canada); Tsang, V.H. [Vancouver Cancer Centre and British Columbia Cancer Agency, Div of Radiation Oncology, BC (Canada); Munk, P.L. [Univ. of British Columbia, Dept. of Radiology and Surgery, Vancouver, BC (Canada); Vancouver Hospital and Health Sciences Centre, Dept. of Radiology, BC (Canada)

    2000-10-01

    To compare magnetic resonance imaging (MRI) and computed tomography (CT) in defining the T stage and full tumour extent of nasopharyngeal carcinoma. Forty-eight patients with pathologically proven nasopharyngeal carcinoma underwent MRI and CT examinations within 2 weeks of each other. Contrast medium was used in both examinations. The T stage and full tumour extent according to MRI and CT were compared. In 32 patients MRI and CT findings agreed completely. MRI findings resulted in assignment of a higher stage than CT findings in another 8 patients. In the remaining 8 patients MRI showed wider tumour spread than CT, although there was no discordance in the T stage assigned. When compared with CT in defining the full tumour extent and assigning the T stage in 48 patients with nasopharyngeal carcinoma, MRI showed more extensive disease in 16 patients, including 8 in whom the T stage was revised upward. Therapy was altered as a result of the MRI findings. (author)

  15. Simulating chiral magnetic effect and anomalous transport phenomena in the pre-equilibrium stages of heavy-ion collisions

    Science.gov (United States)

    Mace, Mark; Mueller, Niklas; Schlichting, Sören; Sharma, Sayantan

    2017-11-01

    We present a first principles approach to study the Chiral Magnetic Effect during the pre-equilibrium stage of a heavy-ion collision. We discuss the dynamics of the Chiral Magnetic Effect and Chiral Magnetic Wave based on real-time lattice simulations with dynamical (Wilson and Overlap) fermions simultaneously coupled to color and electromagnetic fields. While for light quarks we observe a dissipation-less transport of charges as in anomalous hydrodynamics, we demonstrate that for heavier quarks the effects of explicit chiral symmetry breaking lead to a significant reduction of the associated currents.

  16. Rotation and toroidal magnetic field effects on the stability of two-component jets

    Science.gov (United States)

    Millas, Dimitrios; Keppens, Rony; Meliani, Zakaria

    2017-09-01

    Several observations of astrophysical jets show evidence of a structure in the direction perpendicular to the jet axis, leading to the development of 'spine and sheath' models of jets. Most studies focus on a two-component jet consisting of a highly relativistic inner jet and a slower - but still relativistic - outer jet surrounded by an unmagnetized environment. These jets are believed to be susceptible to a relativistic Rayleigh-Taylor-type instability, depending on the effective inertia ratio of the two components. We extend previous studies by taking into account the presence of a non-zero toroidal magnetic field. Different values of magnetization are examined to detect possible differences in the evolution and stability of the jet. We find that the toroidal field, above a certain level of magnetization σ, roughly equal to 0.01, can stabilize the jet against the previously mentioned instabilities and that there is a clear trend in the behaviour of the average Lorentz factor and the effective radius of the jet when we continuously increase the magnetization. The simulations are performed using the relativistic MHD module from the open source, parallel, grid adaptive, mpi-amrvac code.

  17. Using Magnetic Fields to Create and Control High Energy Density Matter

    Energy Technology Data Exchange (ETDEWEB)

    Herrmann, Mark [Sandia National Laboratory

    2012-05-09

    The recently refurbished Z facility at Sandia National Laboratories is the world’s largest pulsed power driver. Z can efficiently deliver currents as large as 26 Million Amperes to centimeter scale loads. These large currents create large magnetic fields that, in turn, create very large pressures in conducting materials. These very large pressures have been used to create unique conditions for high energy density science experiments for a variety of applications. Recently, we have been exploring the use of very strong magnetic fields to significantly relax the requirements for achieving inertial confinement fusion self heating1. The magnetized liner inertial fusion (MagLIF) concept relies on a cylindrically imploding liner, an axial magnetic field, and a laser heated fuel region. We hope to achieve significant fusion yield on the Z facility with this concept. Initial experiments assessing the growth of the Magneto-Rayleigh Taylor instability are promising and recent calculational work has identified an approach to achieving high gain with this concept.

  18. Transcranial magnetic stimulation reveals two functionally distinct stages of motor cortex involvement during perception of emotional body language

    NARCIS (Netherlands)

    Borgomaneri, Sara; Gazzola, Valeria; Avenanti, Alessio

    Studies indicate that perceiving emotional body language recruits fronto-parietal regions involved in action execution. However, the nature of such motor activation is unclear. Using transcranial magnetic stimulation (TMS) we provide correlational and causative evidence of two distinct stages of

  19. Transcranial magnetic stimulation reveals two functionally distinct stages of motor cortex involvement during perception of emotional body language

    NARCIS (Netherlands)

    Borgomaneri, S.; Gazzola, V.; Avenanti, A.

    2015-01-01

    Studies indicate that perceiving emotional body language recruits fronto-parietal regions involved in action execution. However, the nature of such motor activation is unclear. Using transcranial magnetic stimulation (TMS) we provide correlational and causative evidence of two distinct stages of

  20. Identification of cellular infiltrates during early stages of brain inflammation with magnetic resonance microscopy.

    Directory of Open Access Journals (Sweden)

    Helmar Waiczies

    Full Text Available A comprehensive view of brain inflammation during the pathogenesis of autoimmune encephalomyelitis can be achieved with the aid of high resolution non-invasive imaging techniques such as microscopic magnetic resonance imaging (μMRI. In this study we demonstrate the benefits of cryogenically-cooled RF coils to produce μMRI in vivo, with sufficient detail to reveal brain pathology in the experimental autoimmune encephalomyelitis (EAE model. We could visualize inflammatory infiltrates in detail within various regions of the brain, already at an early phase of EAE. Importantly, this pathology could be seen clearly even without the use of contrast agents, and showed excellent correspondence with conventional histology. The cryogenically-cooled coil enabled the acquisition of high resolution images within short scan times: an important practical consideration in conducting animal experiments. The detail of the cellular infiltrates visualized by in vivo μMRI allows the opportunity to follow neuroinflammatory processes even during the early stages of disease progression. Thus μMRI will not only complement conventional histological examination but will also enable longitudinal studies on the kinetics and dynamics of immune cell infiltration.

  1. Different molecular signatures in magnetic resonance imaging-staged facioscapulohumeral muscular dystrophy muscles.

    Directory of Open Access Journals (Sweden)

    Giorgio Tasca

    Full Text Available BACKGROUND: Facioscapulohumeral muscular dystrophy (FSHD is one of the most common muscular dystrophies and is characterized by a non-conventional genetic mechanism activated by pathogenic D4Z4 repeat contractions. By muscle Magnetic Resonance Imaging (MRI we observed that T2-short tau inversion recovery (T2-STIR sequences identify two different conditions in which each muscle can be found before the irreversible dystrophic alteration, marked as T1-weighted sequence hyperintensity, takes place. We studied these conditions in order to obtain further information on the molecular mechanisms involved in the selective wasting of single muscles or muscle groups in this disease. METHODS: Histopathology, gene expression profiling and real time PCR were performed on biopsies from FSHD muscles with different MRI pattern (T1-weighted normal/T2-STIR normal and T1-weighted normal/T2-STIR hyperintense. Data were compared with those from inflammatory myopathies, dysferlinopathies and normal controls. In order to validate obtained results, two additional FSHD samples with different MRI pattern were analyzed. RESULTS: Myopathic and inflammatory changes characterized T2-STIR hyperintense FSHD muscles, at variance with T2-STIR normal muscles. These two states could be easily distinguished from each other by their transcriptional profile. The comparison between T2-STIR hyperintense FSHD muscles and inflammatory myopathy muscles showed peculiar changes, although many alterations were shared among these conditions. CONCLUSIONS: At the single muscle level, different stages of the disease correspond to the two MRI patterns. T2-STIR hyperintense FSHD muscles are more similar to inflammatory myopathies than to T2-STIR normal FSHD muscles or other muscular dystrophies, and share with them upregulation of genes involved in innate and adaptive immunity. Our data suggest that selective inflammation, together with perturbation in biological processes such as neoangiogenesis

  2. Evaluation of carcinoma cervix using magnetic resonance imaging: correlation with clinical FIGO staging and impact on management

    International Nuclear Information System (INIS)

    Dhoot, Nilu Malpani; Bhuyan, Utpal; Kumar, Vinay; Shinagare, Atul; Kataki, Amal Chandra; Barmon, Debabrata

    2012-01-01

    To evaluate carcinoma of the cervix using magnetic resonance imaging (MRI), correlate with clinical approach of International Federation of Gynecology and Obstetrics (FIGO) staging system and to study the impact of MRI findings on patient management. Pathologically confirmed, 75 cases of carcinoma cervix referred to our institute from April 2007 to March 2008 were prospectively studied. Clinical FIGO stage was assigned to each patient by gynaecologists blinded to MRI findings. MRI stage (based on FIGO and TNM) was allotted by radiologists blinded to clinicopathological details. For patients who were operated, histopathological stage was taken as gold standard. For patients who were not operated, gynaecologists decided on a gold standard stage based on all available clinical and imaging data. MR staging was correlated with FIGO staging, with focus on significant alterations in treatment strategy caused due to MRI findings. MRI staging had an accuracy of 89.3% (67/75), while clinical FIGO staging had 61.3% (46/75) accuracy. MRI staging and FIGO staging concurred in 65.6% of the patients and differed in 34.4% of the patients. In about 30.6% (23/75) of the patients, there were relevant additional MRI findings not suspected clinically. The common significant MRI findings were detection of pelvic lymphadenopathy and clinically unsuspected bowel/bladder invasion. The management protocol was significantly altered in 86.9% (20/23) of the patients with additional MRI findings constituting 26.6% (20/75) of the total population. MRI is highly accurate in evaluating carcinoma of the cervix. MRI findings significantly altered therapeutic decisions in 26.6% of the patients. MRI should be considered prior to treatment planning in every patient.

  3. Myometrial invasion and overall staging of endometrial carcinoma: assessment using fusion of T2-weighted magnetic resonance imaging and diffusion-weighted magnetic resonance imaging

    Directory of Open Access Journals (Sweden)

    Guo Y

    2017-12-01

    Full Text Available Yu Guo,1,2 Ping Wang,2 Penghui Wang,2 Wei Gao,1 Fenge Li,3 Xueling Yang,1 Hongyan Ni,2 Wen Shen,2 Zhi Guo1 1Department of Interventional Therapy, Tianjin Medical University Cancer Institute and Hospital, National Clinical Research Center for Cancer, Key Laboratory of Cancer Prevention and Therapy, Tianjin, Tianjin’s Clinical Research Center for Cancer, Tianjin, 2Department of Radiology, Tianjin First Center Hospital, The First Central Clinical College of Tianjin Medical University, Tianjin, 3Department of Gynecology, Tianjin First Center Hospital, Tianjin, People’s Republic of China Background: The age of onset of endometrial carcinoma has been decreasing in recent years. In endometrial carcinoma, it is important to accurately assess invasion depth and preoperative staging. Fusion of T2-weighted magnetic resonance imaging (T2WI and diffusion-weighted magnetic resonance imaging (DWI may contribute to the improvement of anatomical localization of lesions.Materials and methods: In our study, a total of 58 endometrial carcinoma cases were included. Based on the revised 2009 International Federation of Gynecology and Obstetrics staging system, a fusion of T2WI and DWI was utilized for the evaluation of invasion depth and determination of the overall stage. Postoperative pathologic assessment was considered as the reference standard. The consistency of T2WI image staging and pathologic staging, and the consistency of fused T2WI and DWI and pathologic staging were all analyzed using Kappa statistics.Results: Compared with the T2WI group, a significantly higher diagnostic accuracy was observed for myometrial invasion with fusion of T2WI and DWI (77.6% for T2WI; 94.8% for T2WI-DWI. For the identification of deep invasion, we calculated values for diagnostic sensitivity (69.2% for T2WI; 92.3% for T2WI-DWI, specificity (80% for T2WI; 95.6% for T2WI-DWI, positive predictive value (50% for T2WI; 85.7% for T2WI-DWI, and negative predictive value (90% for

  4. AUA Policy Statement on the Use of Multiparametric Magnetic Resonance Imaging in the Diagnosis, Staging and Management of Prostate Cancer.

    Science.gov (United States)

    Fulgham, Pat F; Rukstalis, Daniel B; Turkbey, Ismail Baris; Rubenstein, Jonathan N; Taneja, Samir; Carroll, Peter R; Pinto, Peter A; Bjurlin, Marc A; Eggener, Scott

    2017-10-01

    We summarize the available data about the clinical and economic effectiveness of magnetic resonance imaging in the diagnosis and management of prostate cancer, and provide practical recommendations for its use in the screening, diagnosis, staging and surveillance of prostate cancer. A panel of clinicians with expertise in the diagnosis and management of prostate cancer evaluated the current published literature on the use and effectiveness of magnetic resonance imaging for this disease. When adequate studies were available for analysis, recommendations were made on the basis of data and when adequate studies were not available, recommendations were made on the basis of expert consensus. At this time the data support the use of magnetic resonance imaging in patients with a previous negative biopsy and ongoing concerns about increased risk of prostate cancer. The data regarding its usefulness for initial biopsy suggest a possible role for magnetic resonance imaging in some circumstances. There is currently insufficient evidence to recommend magnetic resonance imaging for screening, staging or surveillance of prostate cancer. Although it adds cost to the management of prostate cancer, magnetic resonance imaging offers superior anatomic detail, and the ability to evaluate cellular density based on water diffusion and blood flow based on contrast enhancement. Imaging targeted biopsy may increase the diagnosis of clinically significant cancers by identifying specific lesions not visible on conventional ultrasound. The clinical indications for the use of magnetic resonance imaging in the management of prostate cancer are rapidly evolving. Copyright © 2017 American Urological Association Education and Research, Inc. Published by Elsevier Inc. All rights reserved.

  5. The association between histological, macroscopic and magnetic resonance imaging assessed synovitis in end-stage knee osteoarthritis

    DEFF Research Database (Denmark)

    Riis, Robert Gabriel Coumine; Gudbergsen, Henrik; Simonsen, Ole

    2017-01-01

    OBJECTIVES: To investigate the association between magnetic resonance imaging (MRI), macroscopic and histological assessments of synovitis in end-stage knee osteoarthritis (KOA). METHODS: Synovitis of end-stage osteoarthritic knees was assessed using non-contrast-enhanced (CE), contrast...... with basic characteristics and non-CE MRI-variables (model 1), after which CE-MRI-variables were added (model 2) with the final model also including DCE-MRI-variables (model 3). RESULTS: 39 patients (56.4% women, mean age 68 years, Kellgren-Lawrence (KL) grade 4) had complete MRI and histological data. Only...

  6. Potentials of high resolution magnetic resonance imaging versus computed tomography for preoperative local staging of colon cancer

    International Nuclear Information System (INIS)

    Rollven, Erik; Blomqvist, Lennart; Holm, Torbjorn; Glimelius, Bengt; Loerinc, Esther

    2013-01-01

    Background: Preoperative identification of locally advanced colon cancer is of importance in order to properly plan treatment. Purpose: To study high resolution T2-weighted magnetic resonance imaging (MRI) versus computed tomography (CT) for preoperative staging of colon cancer with surgery and histopathology as reference standard. Material and Methods: Twenty-eight patients with a total of 29 tumors were included. Patients were examined on a 1.5 T MR unit using a phased array body coil. T2 turbo spin-echo high resolution sequences were obtained in a coronal, transverse, and perpendicular plane to the long axis of the colon at the site of the tumor. Contrast-enhanced CT was performed using a protocol for metastasis staging. The examinations were independently evaluated by two gastrointestinal radiologists using criteria adapted to imaging for prediction of T-stage, N-stage, and extramural venous invasion. Based on the T-stage, tumors were divided in to locally advanced (T3cd-T4) and not locally advanced (T1-T3ab). Surgical and histopathological findings served as reference standard. Results: Using MRI, T-stage, N-stage, and extramural venous invasion were correctly predicted for each observer in 90% and 93%, 72% and 69%, and 82% and 78% of cases, respectively. With CT the corresponding results were 79% and 76%, 72% and 72%, 78% and 67%. For MRI inter-observer agreements (Kappa statistics) were 0.79, 0.10, and 0.76. For CT the corresponding results were 0.64, 0.66, and 0.22. Conclusion: Patients with locally advanced colon cancer, defined as tumor stage T3cd-T4, can be identified by both high resolution MRI and CT, even when CT is performed with a metastasis staging protocol. MRI may have an advantage, due to its high soft tissue discrimination, to identify certain prognostic factors such as T-stage and extramural venous invasion

  7. Potentials of high resolution magnetic resonance imaging versus computed tomography for preoperative local staging of colon cancer

    Energy Technology Data Exchange (ETDEWEB)

    Rollven, Erik; Blomqvist, Lennart [Dept. of Diagnostic Radiology, Karolinska Univ. Hospital Solna, Stockholm (Sweden); Dept. of Molecular Medicine and Surgery, Karolinska Inst., Stockholm (Sweden)], e-mail: erik.rollven@ki.se; Holm, Torbjorn [Dept. of Molecular Medicine and Surgery, Karolinska Inst., Stockholm (Sweden); Dept. of Surgery, Karolinska Univ. Hospital Solna, Stockholm (Sweden); Glimelius, Bengt [Dept. of Radiology, Oncology and Radiation Science, Uppsala Univ., Uppsala (Sweden); Dept. of Oncology and Pathology, Karolinska Inst., Stockholm (Sweden); Loerinc, Esther [Dept. of Oncology and Pathology, Karolinska Inst., Stockholm (Sweden); Dept. of Pathology, Karolinska Univ. Hospital, Solna, Sweden (Sweden)

    2013-09-15

    Background: Preoperative identification of locally advanced colon cancer is of importance in order to properly plan treatment. Purpose: To study high resolution T2-weighted magnetic resonance imaging (MRI) versus computed tomography (CT) for preoperative staging of colon cancer with surgery and histopathology as reference standard. Material and Methods: Twenty-eight patients with a total of 29 tumors were included. Patients were examined on a 1.5 T MR unit using a phased array body coil. T2 turbo spin-echo high resolution sequences were obtained in a coronal, transverse, and perpendicular plane to the long axis of the colon at the site of the tumor. Contrast-enhanced CT was performed using a protocol for metastasis staging. The examinations were independently evaluated by two gastrointestinal radiologists using criteria adapted to imaging for prediction of T-stage, N-stage, and extramural venous invasion. Based on the T-stage, tumors were divided in to locally advanced (T3cd-T4) and not locally advanced (T1-T3ab). Surgical and histopathological findings served as reference standard. Results: Using MRI, T-stage, N-stage, and extramural venous invasion were correctly predicted for each observer in 90% and 93%, 72% and 69%, and 82% and 78% of cases, respectively. With CT the corresponding results were 79% and 76%, 72% and 72%, 78% and 67%. For MRI inter-observer agreements (Kappa statistics) were 0.79, 0.10, and 0.76. For CT the corresponding results were 0.64, 0.66, and 0.22. Conclusion: Patients with locally advanced colon cancer, defined as tumor stage T3cd-T4, can be identified by both high resolution MRI and CT, even when CT is performed with a metastasis staging protocol. MRI may have an advantage, due to its high soft tissue discrimination, to identify certain prognostic factors such as T-stage and extramural venous invasion.

  8. Spleen dynamic contrast-enhanced magnetic resonance imaging as a new method for staging liver fibrosis in a piglet model.

    Directory of Open Access Journals (Sweden)

    Li Zhou

    Full Text Available OBJECTIVE: To explore spleen hemodynamic alteration in liver fibrosis with dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI, and to determine how to stage liver fibrosis with spleen DCE-MRI parameters. MATERIALS AND METHODS: Sixteen piglets were prospectively used to model liver fibrosis staged by liver biopsy, and underwent spleen DCE-MRI on 0, 5th, 9th, 16th and 21st weekend after modeling this disease. DCE-MRI parameters including time to peak (TTP, positive enhancement integral (PEI, maximum slope of increase (MSI and maximum slope of decrease (MSD of spleen were measured, and statistically analyzed to stage this disease. RESULTS: Spearman's rank correlation tests showed that TTP tended to increase with increasing stages of liver fibrosis (r = 0.647, P0.05, and decreased from stage 2 to 4 (P0.05. Mann-Whitney tests demonstrated that TTP and PEI could classify fibrosis between stage 0 and 1-4, between 0-1 and 2-4, between 0-2 and 3-4, or between 0-3 and 4 (all P<0.01. MSD could discriminate between 0-2 and 3-4 (P = 0.006, or between 0-3 and 4 (P = 0.012. MSI could not differentiate between any two stages. Receiver operating characteristic analysis illustrated that area under receiver operating characteristic curve (AUC of TTP was larger than of PEI for classifying stage ≥1 and ≥2 (AUC = 0.851 and 0.783, respectively. PEI could best classify stage ≥3 and 4 (AUC = 0.903 and 0.96, respectively. CONCLUSION: Spleen DCE-MRI has potential to monitor spleen hemodynamic alteration and classify liver fibrosis stages.

  9. Filament formation in wind-cloud interactions- II. Clouds with turbulent density, velocity, and magnetic fields

    Science.gov (United States)

    Banda-Barragán, W. E.; Federrath, C.; Crocker, R. M.; Bicknell, G. V.

    2018-01-01

    We present a set of numerical experiments designed to systematically investigate how turbulence and magnetic fields influence the morphology, energetics, and dynamics of filaments produced in wind-cloud interactions. We cover 3D, magnetohydrodynamic systems of supersonic winds impacting clouds with turbulent density, velocity, and magnetic fields. We find that lognormal density distributions aid shock propagation through clouds, increasing their velocity dispersion and producing filaments with expanded cross-sections and highly magnetized knots and subfilaments. In self-consistently turbulent scenarios, the ratio of filament to initial cloud magnetic energy densities is ∼1. The effect of Gaussian velocity fields is bound to the turbulence Mach number: Supersonic velocities trigger a rapid cloud expansion; subsonic velocities only have a minor impact. The role of turbulent magnetic fields depends on their tension and is similar to the effect of radiative losses: the stronger the magnetic field or the softer the gas equation of state, the greater the magnetic shielding at wind-filament interfaces and the suppression of Kelvin-Helmholtz instabilities. Overall, we show that including turbulence and magnetic fields is crucial to understanding cold gas entrainment in multiphase winds. While cloud porosity and supersonic turbulence enhance the acceleration of clouds, magnetic shielding protects them from ablation and causes Rayleigh-Taylor-driven subfilamentation. Wind-swept clouds in turbulent models reach distances ∼15-20 times their core radius and acquire bulk speeds ∼0.3-0.4 of the wind speed in one cloud-crushing time, which are three times larger than in non-turbulent models. In all simulations, the ratio of turbulent magnetic to kinetic energy densities asymptotes at ∼0.1-0.4, and convergence of all relevant dynamical properties requires at least 64 cells per cloud radius.

  10. Magnetic Resonance Imaging Staging to Evaluate the Stability of Capitellar Osteochondritis Dissecans Lesions.

    Science.gov (United States)

    Itsubo, Toshiro; Murakami, Narumichi; Uemura, Kazutaka; Nakamura, Koichi; Hayashi, Masanori; Uchiyama, Shigeharu; Kato, Hiroyuki

    2014-08-01

    Treatment for capitellar osteochondritis dissecans (COCD) lesions is usually based on their stability from the bony floor after arthroscopic or open direct observation. Thus, a noninvasive means of lesion stability assessment by use of imaging is desirable to preoperatively determine treatment strategy. To evaluate our modified MRI staging system for COCD, we compared the results of MRI staging with the International Cartilage Repair Society (ICRS) classification for lesion stability. Intra- and interrater reliability for MRI staging was examined as well. Cohort study (diagnosis); Level of evidence, 2. Fifty-two COCD lesions were preoperatively evaluated by T2-weighted MRI and classified into 5 stages: stage 1 = normally shaped capitellum with several spotted areas of high signal intensity that is lower than that of cartilage; stage 2 = as with stage 1 but with several spotted areas of higher intensity than that of cartilage; stage 3 = as with stage 2 but with both discontinuity and noncircularity of the chondral surface signal of the capitellum and no high signal interface apparent between the lesion and the floor; stage 4 = lesion separated by a high intensity line in comparison with cartilage; and stage 5 = capitellar lesion displaced from the floor or defect of the capitellar lesion noted. The MRI staging results were compared with the intraoperative ICRS classification for lesion stability of each patient. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were all determined for fragment instability. Intra- and interrater correlations for our MRI staging were calculated among 3 examiners. Preoperative MRI grading correctly matched ICRS classification in 49 of 52 patients (94%), with a sensitivity of 100% and a specificity of 80%. The PPV and NPV were 93% and 100%, respectively, for diagnosing lesion instability. Intrarater reliability (intraclass correlation coefficient [ICC]) for MRI staging was high at ICC(1, 1

  11. Enhancing Understanding of Magnetized High Energy Density Plasmas from Solid Liner Implosions Using Fluid Modeling with Kinetic Closures

    Science.gov (United States)

    Masti, Robert; Srinivasan, Bhuvana; King, Jacob; Stoltz, Peter; Hansen, David; Held, Eric

    2017-10-01

    Recent results from experiments and simulations of magnetically driven pulsed power liners have explored the role of early-time electrothermal instability in the evolution of the MRT (magneto-Rayleigh-Taylor) instability. Understanding the development of these instabilities can lead to potential stabilization mechanisms; thereby providing a significant role in the success of fusion concepts such as MagLIF (Magnetized Liner Inertial Fusion). For MagLIF the MRT instability is the most detrimental instability toward achieving fusion energy production. Experiments of high-energy density plasmas from wire-array implosions have shown the requirement for more advanced physics modeling than that of ideal magnetohydrodynamics. The overall focus of this project is on using a multi-fluid extended-MHD model with kinetic closures for thermal conductivity, resistivity, and viscosity. The extended-MHD model has been updated to include the SESAME equation-of-state tables and numerical benchmarks with this implementation will be presented. Simulations of MRT growth and evolution for MagLIF-relevant parameters will be presented using this extended-MHD model with the SESAME equation-of-state tables. This work is supported by the Department of Energy Office of Science under Grant Number DE-SC0016515.

  12. Instability growth for magnetized liner inertial fusion seeded by electro-thermal, electro-choric, and material strength effects

    International Nuclear Information System (INIS)

    Pecover, J. D.; Chittenden, J. P.

    2015-01-01

    A critical limitation of magnetically imploded systems such as magnetized liner inertial fusion (MagLIF) [Slutz et al., Phys. Plasmas 17, 056303 (2010)] is the magneto-Rayleigh-Taylor (MRT) instability which primarily disrupts the outer surface of the liner. MagLIF-relevant experiments have showed large amplitude multi-mode MRT instability growth growing from surface roughness [McBride et al., Phys. Rev. Lett. 109, 135004 (2012)], which is only reproduced by 3D simulations using our MHD code Gorgon when an artificially azimuthally correlated initialisation is added. We have shown that the missing azimuthal correlation could be provided by a combination of the electro-thermal instability (ETI) and an “electro-choric” instability (ECI); describing, respectively, the tendency of current to correlate azimuthally early in time due to temperature dependent Ohmic heating; and an amplification of the ETI driven by density dependent resistivity around vapourisation. We developed and implemented a material strength model in Gorgon to improve simulation of the solid phase of liner implosions which, when applied to simulations exhibiting the ETI and ECI, gave a significant increase in wavelength and amplitude. Full circumference simulations of the MRT instability provided a significant improvement on previous randomly initialised results and approached agreement with experiment

  13. No Escape from the Supernova! Magnetic Imprisonment of Dusty Pinballs by a Supernova Remnant arXiv

    CERN Document Server

    Fry, Brian J.; Ellis, John R.

    Motivated by recent measurements of deposits of $^{60}$Fe on the ocean floor and the lunar surface, we model the transport of dust grains containing $^{60}$Fe from a near-Earth (i.e., within 100 pc) supernova (SN). We inject dust grains into the environment of a SN remnant (SNR) and trace their trajectories using a magnetohydrodynamic description. We assume the interstellar medium (ISM) magnetic fields are turbulent, and are amplified by the SNR shock, while the SN wind and ejecta fields are negligible. We examine the various influences on the dust grains within the SNR to determine when/if the dust decouples from the plasma, how much it is sputtered, and where within the SNR the dust grains are located. We find that Rayleigh-Taylor instabilities are important for dust survival, as they influence the location of the SN's reverse shock. We find that the presence of a magnetic field within the shocked ISM material limits the passage of SN dust grains, with the field either reflecting or trapping the grains with...

  14. Multiparametric magnetic resonance imaging for pre-treatment local staging of prostate cancer: A Cancer Care Ontario clinical practice guideline

    Science.gov (United States)

    Salerno, Jennifer; Finelli, Antonio; Morash, Chris; Morgan, Scott C.; Power, Nicholas; Schieda, Nichola; Haider, Masoom A.

    2016-01-01

    Introduction: The utility of T2-weighted magnetic resonance imaging (MRI) in the local staging of prostate cancer is controversial. Due to the success of multiparametric MRI in cancer localization, there is renewed interested in MRI (± functional sequences) for local staging. Guidance on pre-treatment local staging of prostate cancer by MRI was developed using systematic review methodology and expert consultation. Methods: MEDLINE, EMBASE, Cochrane Database of Systematic Reviews, and other databases were searched to identify studies comparing: (1) MRI staging vs. radical prostatectomy staging on diagnostic accuracy outcomes; and (2) MRI staging vs. routine clinical staging on clinical and patient outcomes. Studies meeting inclusion criteria were synthesized by outcome and sensitivity/specificity analysis by tumour location was performed. Evidence quality of included studies was assessed and considered in recommendation formulation. Results: The literature search identified 2510 citations; 62 studies were included. Analysis of MRI ≥1.5 T plus endorectal coil (ER) (± functional sequences) in the detection of extraprostatic extension or seminal vesicle invasion showed modest sensitivities (≥50%) and excellent specificities (>85%) among patients scheduled for radical prostatectomy. MRI upstaging was shown in 20/21 studies, with large variation in correctness (11–85%). Scarcity of clinical and patient outcomes among studies limited synthesis and evaluation. Quality assessment found non-trivial biases. Conclusions: Modest imaging performance was shown for MRI (1.5 T + ER and 3 T ± ER) ± functional sequences in regards to sensitivity. Limitations in study design, reporting of clinical and patient outcomes, and the heterogeneous use of MRI tempered the strength of the recommendations. PMID:27800062

  15. Dependence of developing magnetic hysteresis characteristics on stages of evolving microstructure in polycrystalline yttrium iron garnet

    International Nuclear Information System (INIS)

    Rodziah, N.; Hashim, M.; Idza, I.R.; Ismayadi, I.; Hapishah, A.N.; Khamirul, M.A.

    2012-01-01

    The microstructure evolution in several polycrystalline yttrium iron garnet samples as a result of a sintering scheme was studied in detail, in parallel with the changes in their magnetic properties. Samples with nanometer sized starting powder were synthesized by employing the High-Energy Ball Milling technique and then sintering toroidal compacts of the milled powder. Nine sintered samples were obtained, each corresponding to a particular sintering from 600 °C to 1400 °C. The samples were characterized for their evolution in crystalline phases, microstructure and magnetic hysteresis-loops parameters. The results showed an increasing tendency of the saturation magnetization and saturation induction with grain size, which is attributed to crystallinity increase and to reduction of demagnetizing fields in the grains. The variation in coercivity could be related to anisotropy field changes within the samples due to grain size changes. In particular, the starting appearance of room temperature ferromagnetic order suggested by the sigmoid-shaped B-H loops seems to be dependent on a sufficient number of large enough magnetic domain-containing grains having been formed in the microstructure. Viewed simultaneously, the hysteresis loops appear to belong to three groups with different magnetism-type dominance, respectively dependent on phase purity and three different groups of grain size distributions.

  16. Effects of Repetitive Transcranial Magnetic Stimulation on Behavioral Recovery during Early Stage of Traumatic Brain Injury in Rats.

    Science.gov (United States)

    Yoon, Kyung Jae; Lee, Yong-Taek; Chung, Pil-Wook; Lee, Yun Kyung; Kim, Dae Yul; Chun, Min Ho

    2015-10-01

    Repetitive transcranial magnetic stimulation (rTMS) is a promising technique that modulates neural networks. However, there were few studies evaluating the effects of rTMS in traumatic brain injury (TBI). Herein, we assessed the effectiveness of rTMS on behavioral recovery and metabolic changes using brain magnetic resonance spectroscopy (MRS) in a rat model of TBI. We also evaluated the safety of rTMS by measuring brain swelling with brain magnetic resonance imaging (MRI). Twenty male Sprague-Dawley rats underwent lateral fluid percussion and were randomly assigned to the sham (n=10) or the rTMS (n=10) group. rTMS was applied on the fourth day after TBI and consisted of 10 daily sessions for 2 weeks with 10 Hz frequency (total pulses=3,000). Although the rTMS group showed an anti-apoptotic effect around the peri-lesional area, functional improvements were not significantly different between the two groups. Additionally, rTMS did not modulate brain metabolites in MRS, nor was there any change of brain lesion or edema after magnetic stimulation. These data suggest that rTMS did not have beneficial effects on motor recovery during early stages of TBI, although an anti-apoptosis was observed in the peri-lesional area.

  17. Preliminary investigation on the use of low current pulsed power Z-pinch plasma devices for the study of early stage plasma instabilities

    Science.gov (United States)

    Kaselouris, E.; Dimitriou, V.; Fitilis, I.; Skoulakis, A.; Koundourakis, G.; Clark, E. L.; Chatzakis, J.; Bakarezos, Μ; Nikolos, I. K.; Papadogiannis, N. A.; Tatarakis, M.

    2018-01-01

    This article addresses key features for the implementation of low current pulsed power plasma devices for the study of matter dynamics from the solid to the plasma phase. The renewed interest in such low current plasma devices lies in the need to investigate methods for the mitigation of prompt seeding mechanisms for the generation of plasma instabilities. The low current when driven into thick wires (skin effect mode) allows for the simultaneous existence of all phases of matter from solid to plasma. Such studies are important for the concept of inertial confinement fusion where the mitigation of the instability seeding mechanisms arising from the very early moments within the target’s heating is of crucial importance. Similarly, in the magnetized liner inertial fusion concept it is an open question as to how much surface non-uniformity correlates with the magneto-Rayleigh-Taylor instability, which develops during the implosion. This study presents experimental and simulation results, which demonstrate that the use of low current pulsed power devices in conjunction with appropriate diagnostics can be important for studying seeding mechanisms for the imminent generation of plasma instabilities in future research.

  18. The potential of imposed magnetic fields for enhancing ignition probability and fusion energy yield in indirect-drive inertial confinement fusion

    Science.gov (United States)

    Perkins, L. J.; Ho, D. D.-M.; Logan, B. G.; Zimmerman, G. B.; Rhodes, M. A.; Strozzi, D. J.; Blackfield, D. T.; Hawkins, S. A.

    2017-06-01

    We examine the potential that imposed magnetic fields of tens of Tesla that increase to greater than 10 kT (100 MGauss) under implosion compression may relax the conditions required for ignition and propagating burn in indirect-drive inertial confinement fusion (ICF) targets. This may allow the attainment of ignition, or at least significant fusion energy yields, in presently performing ICF targets on the National Ignition Facility (NIF) that today are sub-marginal for thermonuclear burn through adverse hydrodynamic conditions at stagnation [Doeppner et al., Phys. Rev. Lett. 115, 055001 (2015)]. Results of detailed two-dimensional radiation-hydrodynamic-burn simulations applied to NIF capsule implosions with low-mode shape perturbations and residual kinetic energy loss indicate that such compressed fields may increase the probability for ignition through range reduction of fusion alpha particles, suppression of electron heat conduction, and potential stabilization of higher-mode Rayleigh-Taylor instabilities. Optimum initial applied fields are found to be around 50 T. Given that the full plasma structure at capsule stagnation may be governed by three-dimensional resistive magneto-hydrodynamics, the formation of closed magnetic field lines might further augment ignition prospects. Experiments are now required to further assess the potential of applied magnetic fields to ICF ignition and burn on NIF.

  19. [Correlation of imaging-based staging to prognosis of nasopharyngeal carcinoma: computed tomography versus magnetic resonance imaging].

    Science.gov (United States)

    Hu, Dan; Cao, Ka-Jia; Xie, Guo-Feng; Huang, Pei-Yu; Wang, Cheng-Tao; Zhang, Ying-Ying

    2008-07-01

    Imaging results are important for clinical staging and irradiation target planning of nasopharyngeal carcinoma (NPC). This study tried to analyze the correlations of staging based on computed tomography (CT) and magnetic resonance imaging (MRI) before radiotherapy to prognosis of NPC. Clinical data of 445 pathologically confirmed NPC patients with no metastasis were analyzed. CT was performed on 230 patients before treatmentû MRI was performed on 215 patients. All patients received conventional radiotherapy, and some locally advanced patients received additional chemotherapy. Kaplan-Meier and log-rank tests were used to analyze and compare the survival rates of the two groups. Cox model was used to analyze prognostic factors. The 1-, 2-, and 3-year overall survival rates were significantly lower in CT group than in MRI group (96.9% vs. 98.6%, 90.3% vs. 94.3%, 85.3% vs. 92.3%, Chi2 =6.305, P=0.012). The 1-, 2-, and 3-year disease-free and relapse-free survival rates were also significantly lower in CT group than in MRI group (P<0.05). Univariate analysis showed that clinical stage, N stage, imaging method and chemotherapy were prognostic factors of NPC. Multivariate analysis showed that clinical stage and imaging method were independent prognostic factors of NPC. Determining target volume by MRI before radiotherapy can improve the survival rate and local control rate of NPC patients when compared with CT. Clinical stage and imaging method are independent prognostic factors of NPC patients.

  20. Sausage instabilities on top of kinking lengthening current-carrying magnetic flux tubes

    Science.gov (United States)

    von der Linden, Jens; You, Setthivoine

    2017-05-01

    We theoretically explore the possibility of sausage instabilities developing on top of a kink instability in lengthening current-carrying magnetic flux tubes. Observations indicate that the dynamics of magnetic flux tubes in our cosmos and terrestrial experiments can involve topological changes faster than time scales predicted by resistive magnetohydrodynamics. Recent laboratory experiments suggest that hierarchies of instabilities, such as kink and Rayleigh-Taylor, could be responsible for initiating fast topological changes by locally accessing two-fluid and kinetic regimes. Sausage instabilities can also provide this coupling mechanism between disparate scales. Flux tube experiments can be classified by the flux tube's evolution in a configuration space described by a normalized inverse aspect-ratio k ¯ and current-to-magnetic flux ratio λ ¯ . A lengthening current-carrying magnetic flux tube traverses this k ¯ - λ ¯ space and crosses stability boundaries. We derive a single general criterion for the onset of the sausage and kink instabilities in idealized magnetic flux tubes with core and skin currents. The criterion indicates a dependence of the stability boundaries on current profiles and shows overlapping kink and sausage unstable regions in the k ¯ - λ ¯ space with two free parameters. Numerical investigation of the stability criterion reduces the number of free parameters to a single one that describes the current profile and confirms the overlapping sausage and kink unstable regions in k ¯ - λ ¯ space. A lengthening, ideal current-carrying magnetic flux tube can therefore become sausage unstable after it becomes kink unstable.

  1. Modeling the fine fragmentation following the triggering stage of a vapor explosion; Modelisation de la fragmentaton fine lors de la phase de declenchement d`une explosion de vapeur

    Energy Technology Data Exchange (ETDEWEB)

    Darbord, I. [CEA Grenoble, 38 (France). Service d`Etudes et de Modelisation Thermohydraulique

    1997-06-11

    In the frame of PWR severe accidents, where the core melt, this thesis studies one of the stages of an FCI (fuel coolant interaction) or vapor explosion. An FCI is a rapid evaporation of a coolant when it comes into contact with a hot liquid. More precisely, the subject of this study is the triggering stage of the FCI, when a fuel drop of diameter around one centimeter breaks up into many fragments, diameter of which is around a hundred micrometers. The model describes the cyclic collapse and growth of a vapor bubble around the fuel droplet and its fragmentation. The main features of the model are: - the destabilization of the film or the vapor bubble due to the growth of Rayleigh-Taylor instabilities (those form coolant jets that contact the fuel surface); - The mechanisms of fragmentation, following the contacts (in the case of entrapment of a certain amount of coolant in the fuel, the entrapped coolant evaporates violently after it has been heated to the homogeneous nucleation temperature); - the transient heat transfer from the fragments to the coolant and the elevated vapor production, which leads to an important expansion of the bubble (about this point, the cooling of the fragments has been described by a transient heat transfer coefficient linked to nucleate boiling). The results of the model show good agreement with experimental data. (Author) 68 refs.

  2. Impact of neoadjuvant therapy in downstaging of lower rectal adenocarcinoma and the role of pelvic magnetic resonance in staging.

    Science.gov (United States)

    Magri, Karina Dagre; Bin, Fang Chia; Formiga, Fernanda Bellotti; Manzione, Thiago da Silveira; Gomes, Caroline Merci Caliari de Neves; Candelári, Paulo de Azeredo Passos; Ortiz, Jorge Alberto; Klug, Wilmar Artur; Mandia, José; Capelhuchnik, Peretz

    2016-01-01

    to evaluate the effect of neoadjuvant therapy on the stage (TNM) of patients with rectal adenocarcinoma and validate the use of MRI as a method of determining locoregional stage. we conducted a retrospective study of 157 patients with lower rectum adenocarcinoma, whom we divided into two groups: Group 1, 81 patients (52%) who had undergone surgical treatment initially, with the purpose to analyze the accuracy of locoregional staging by pelvic magnetic resonance imaging throug the comparison of radiological findings with pathological ones; Group 2, 76 patients (48%), who had been submitted to neoadjuvant therapy (chemotherapy and radiation) prior to definitive surgical treatment, so as to evaluate its effects on the stage by comparing clinical and radiological findings with pathology. In group 1, the accuracy of determining tumor depth (T) and lymph node involvement (N) was 91.4% and 82.7%, respectively. In group 2, neoadjuvant therapy decreased the T stage, N stage and TNM stage in 51.3%, 21% and 48.4% of cases, respectively. neoadjuvant therapy in patients with rectal adenocarcinoma is effective in decreasing disease stage, and pelvic magnetic resonance imaging is effective for locoregional staging. avaliar o efeito da terapia neoadjuvante, nos pacientes portadores de adenocarcinoma de reto, sobre o estádio (TNM) e validar o emprego da ressonância magnética como método de determinação do estádio locorregional. estudo retrospectivo de 157 pacientes com diagnóstico de adenocarcinoma de reto baixo, que foram divididos em dois grupos: Grupo 1, 81 pacientes (52%), submetidos ao tratamento cirúrgico de princípio, cuja finalidade foi analisar a acurácia da determinação do estádio locorregional pela ressonância magnética da pelve, através da comparação entre os achados radiológicos e os achados anatomopatológicos; Grupo 2, 76 pacientes (48%), encaminhados à terapia neoadjuvante (quimioterapia e radioterapia), antes do tratamento cirúrgico definitivo

  3. Influence of Electric, Magnetic, and Electromagnetic Fields on the Circadian System: Current Stage of Knowledge

    Science.gov (United States)

    Żak, Arkadiusz

    2014-01-01

    One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms—two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields. PMID:25136557

  4. Influence of electric, magnetic, and electromagnetic fields on the circadian system: current stage of knowledge.

    Science.gov (United States)

    Lewczuk, Bogdan; Redlarski, Grzegorz; Zak, Arkadiusz; Ziółkowska, Natalia; Przybylska-Gornowicz, Barbara; Krawczuk, Marek

    2014-01-01

    One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms-two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields.

  5. Influence of Electric, Magnetic, and Electromagnetic Fields on the Circadian System: Current Stage of Knowledge

    Directory of Open Access Journals (Sweden)

    Bogdan Lewczuk

    2014-01-01

    Full Text Available One of the side effects of each electrical device work is the electromagnetic field generated near its workplace. All organisms, including humans, are exposed daily to the influence of different types of this field, characterized by various physical parameters. Therefore, it is important to accurately determine the effects of an electromagnetic field on the physiological and pathological processes occurring in cells, tissues, and organs. Numerous epidemiological and experimental data suggest that the extremely low frequency magnetic field generated by electrical transmission lines and electrically powered devices and the high frequencies electromagnetic radiation emitted by electronic devices have a potentially negative impact on the circadian system. On the other hand, several studies have found no influence of these fields on chronobiological parameters. According to the current state of knowledge, some previously proposed hypotheses, including one concerning the key role of melatonin secretion disruption in pathogenesis of electromagnetic field induced diseases, need to be revised. This paper reviews the data on the effect of electric, magnetic, and electromagnetic fields on melatonin and cortisol rhythms—two major markers of the circadian system as well as on sleep. It also provides the basic information about the nature, classification, parameters, and sources of these fields.

  6. [Nuclear Magnetic Resonance Imaging in the staging of adenocarcinoma of the uterine cervix].

    Science.gov (United States)

    Pellegrino, A; Cormio, G; Maneo, A; Vanzulli, A; Villa, G; Lissoni, A; Landoni, F

    1995-12-01

    Clinical staging is often inaccurate in the evaluation of local extension of cervical carcinoma. In the present study the sensivity of MR imaging in predicting extracervical tumor invasion on the basis of the detection of a thinning of the univolved cervical stromal ring (3 mm or less) was compared to the sensivity achieved by direct visualization of a complete stomal interruption. Fifteen consecutive patients with adenocarcinoma of the uterine cervix (FIGO stage Ib-IIa), were examined with axial and sagittal weighed MR sequences. Pathologic proof after hysterectomy was obtained in all subjects. The sensitivity in predicting extracervical involvement on the basis of the MR Imaging visualization of a thinned stroma was 83%, whereas the sensitivity obtained by detection of a complete stromal interruption was 50%. Among women with a spared cervical stroma of more than 3 mm at MR Imaging, only one had at pathologic examination microscopic metastasis in a parametrial lymphnode, accounting for a negative predictivity value of 87%. The results of our study points out a high concordance between MR Imaging findings and pathologic results, and indicate that the detection of a intact cervical stromal ring exceeding 3 mm at MR imaging is related to a very low risk of extracervical seeding of tumor. On the other side, the detection of a thinned stromal ring is related to a high incidence of parametrial invasion. The information obtained by this imaging technique may therefore be extremely useful in the accurate tailoring of treatment for these patients.

  7. Prospective, blinded trial of whole-body magnetic resonance imaging versus computed tomography positron emission tomography in staging primary and recurrent cancer of the head and neck.

    LENUS (Irish Health Repository)

    O'Neill, J P

    2012-02-01

    OBJECTIVES: To compare the use of computed tomography - positron emission tomography and whole-body magnetic resonance imaging for the staging of head and neck cancer. PATIENTS AND METHODS: From January to July 2009, 15 consecutive head and neck cancer patients (11 men and four women; mean age 59 years; age range 19 to 81 years) underwent computed tomography - positron emission tomography and whole-body magnetic resonance imaging for pre-therapeutic evaluation. All scans were staged, as per the American Joint Committee on Cancer tumour-node-metastasis classification, by two blinded consultant radiologists, in two sittings. Diagnoses were confirmed by histopathological examination of endoscopic biopsies, and in some cases whole surgical specimens. RESULTS: Tumour staging showed a 74 per cent concordance, node staging an 80 per cent concordance and metastasis staging a 100 per cent concordance, comparing the two imaging modalities. CONCLUSION: This study found radiological staging discordance between the two imaging modalities. Whole-body magnetic resonance imaging is an emerging staging modality with superior visualisation of metastatic disease, which does not require exposure to ionising radiation.

  8. [Clinical randomized controlled trial on ultrashort wave and magnetic therapy for the treatment of early stage distal radius fractures].

    Science.gov (United States)

    Wang, Guan-Jie; Liu, Jia

    2012-07-01

    To explore the effect of application of ultrashort wave and magnetic therapy instrument on the swelling regression in distal radius fractures treated by splint external fixation in initial stage. From March 2007 to May 2010,90 patients with distal radial fracture were treated by manual reduction and splint external fixation. After manual reduction and small splints external fixation, these patients were randomly divided into electrical physical therapy group, western medicine group and the control group by the order of calling number, with 30 cases each group. In control group, there were 9 males and 21 females with an average age of (61.29 +/- 1.97) years, the patients raised and exercise the limb and fingers only. The other two groups also carried out this treatment. In electrical physical therapy group, there were 9 males and 21 females with an average age of (62.37 +/- 2.48) years, the patients were treated with ultrashort wave and magnetic therapy instrument for early intervention, once a day, 5 days for a course of treatment and three cycle were operated. In western medicine group,there were 8 males and 22 females with an average age of (60.12 +/- 2.87) years, the patients were injected with beta-aescin (20 mg, intravenous injection,once a day) for 5 days, followed by Danshen injection (20 ml, intravenous injection, once a day) for 10 days. The limb swelling of patients were assessed every day for 20 days after manual reduction and small splints external fixation. The time of swelling regression in electrical physical therapy group, western medicine group and the control group were respectively (9.62 +/- 3.32), (10.05 +/- 3.05) and (14.57 +/- 2.93) days. Both of that in electrical physical therapy group and western medicine group were shorter than that in the control group (P0.05). The effective rate of swelling regression in electrical physical therapy group, western medicine group and the control group were 86.67%, 80.00%, 46.66% respectively. There was no

  9. Equinox transition at the magnetic equator in Africa: analysis of ESF ionograms

    Directory of Open Access Journals (Sweden)

    B. J.-P. Adohi

    2008-06-01

    Full Text Available We study equatorial night-time F layer behaviour from quarter-hourly ionograms at Korhogo/Ivory Coast (9.2° N, 5° W, dip lat. −2.4° during local Spring March–April 1995, declining solar flux period, according to the magnetic activity. The height and thickness of the F-layer are found to vary intensely with time and from one day to the next. At time of the equinox transition, by the end of March, a net change of the nightly height-time variation is observed. The regime of a single height peak phase before 22 March changes to up to three main F-layer height phases after 30 March, each associated to a dominant mechanism. The first phase is identified to the post-sunset E×B pulse, the second phase associated to a change in the wind circulation phenomenon and the third one attributed to pre-sunrise phenomena. The influence of the magnetic activity is identified by the increase in the second peak amplitude. After the 21 April magnetic-equinox period, the height-time morphology becomes more irregular suggesting meridional wind abatement. The initiation, the growth and the maintenance of ESF are explored in relation to these nightly variations. The Rayleigh-Taylor instability is clearly identified as main precursor phenomenon. This is followed by the P-type (F-layer peak spread structures, the whole with no specific dependence on the magnetic activity and on the F-layer phases, in contrast to further I and F-type (Inside and Frequency spread ESFs. We discuss our results in the light of recent advanced experiments in Peru and the pacific.

  10. New construction of the magnetohydrodynamic spectrum of stationary plasma flows. II. Rayleigh-Taylor and Kelvin-Helmholtz instability

    NARCIS (Netherlands)

    Goedbloed, J. P.

    2009-01-01

    In a preceding paper [J. P. Goedbloed, Phys. Plasmas 16, 122110 (2009)] a new method was developed to compute the magnetohydrodynamic spectrum of waves and instabilities of stationary plasma flows by means of the construction of the solution paths, P-s and P-u, of stable waves and instabilities in

  11. Multi-modal investigations of compressible Rayleigh-Taylor instability in stratified media Project: w17_multirti

    Energy Technology Data Exchange (ETDEWEB)

    Livescu, Daniel [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Wieland, Scott A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Univ. of Colorado, Boulder, CO (United States); Reckinger, Scott [Montana State Univ., Bozeman, MT (United States)

    2018-02-27

    The simulations compare, for the first time, three practically important background stratifications under thermal equilibrium and out of equilibrium (isentropic, isopycnic) and show significant differences on the instability growth

  12. Stabilization of the Rayleigh-Taylor instability by convection and thermal conduction in smooth density gradient: WKB analysis

    International Nuclear Information System (INIS)

    Bud'ko, A.B.; Liberman, M.A.; Bondarenko, E.A.

    1992-01-01

    Since development of the RT modes in the ablatively accelerated plasma of laser targets imposes crucial limitations on symmetry of spherical implosions and hence on energy cumulation, it has been the subject of intensive numerical and analytical analysis in the recent years, particularly in the context of inertial confinement fusion. Recent thin-foil ablative-acceleration experiments as well as the results of 2D numerical simulations demonstrated substantial reduction of the instability growth rates compared with the classical theory predictions up to the total stabilization in the short-wavelength limit. The numerical results indicated that the main stabilization mechanism is convection. To derive the scaling laws for the RT growth rates and cut-off wavenumbers in the wide range of flow parameters, analytical solutions attract special interest. The analytical approach based on the discontinuity model was developed to analyze the reduction of the RT growth rates by the plasma convective flow and the thermal conductivity effects. The following major problem arises in the discontinuity approximation, which leaves the solution undetermined: the number of the boundary conditions on the perturbed ablation surface is not sufficient to derive the dispersion equation. One needs additional boundary conditions not associated with the conservation laws on the discontinuity surface to close the system of linearized equations for small perturbations. The stabilization effect of highly structured hydrodynamic profiles was studied by Mikaelian and Munro for a stationary plasma. Nevertheless, no reasonable analytical model was constructed taking into account the combined convective, thermal conductivity and density gradient reduction of the RT growth rates. In this report we develop the analytical approach based on the WKB approximation to analyze the stabilization of the RT modes in plasma with smooth density and velocity gradients. (author) 9 refs., 1 fig

  13. Examining the Electric Fields of the Evening Equatorial Ionosphere When the Solar Terminator is Aligned and Not Aligned with the Magnetic Meridian

    Science.gov (United States)

    Eccles, J. V.

    2014-12-01

    The electric field structure of the equatorial ionosphere near sunset has implications on the development of plasma irregularities. The details of the development of the electric fields are examined using a global ionosphere-electrodynamics model. The results of simulations of simplified conditions show the influence of the arrangement of the solar terminator with the magnetic meridian. The relationships of the Curl-Free mechanism, the Hall Current Divergence mechanism, and the role of the Equatorial Electorjet region control the magnitude and timing of the Prereversal Enhancement of the zonal electric field as well as its altitude profile above the F region bottomside. Realistic conditions for 'equinox' and 'solstice' solar terminator arrangments are presented. The stability of the low-latitude ionosphere has a demonstrated relationship with the solar terminator alignment [Tsunoda, JGR, 1981]. The profile of the vertical and zonal electric field below the bottomside is then examined using the global model to explore the controlling elements of the electric field structure and the growth rates of the Rayleigh-Taylor instability and Collisional Shear instability.Tsunoda, R. T. (1985), Control of the seasonal and longitudinal occurrence of equatorial scintillations by the longitudinal gradient in integrated E region Pedersen conductivity, J. Geophys. Res., 90(A1),447-456, doi:10.1029/JA090iA01p00447.

  14. Concept of a staged FEL enabled by fast synchrotron radiation cooling of laser-plasma accelerated beam by solenoidal magnetic fields in plasma bubble

    Science.gov (United States)

    Seryi, Andrei; Lesz, Zsolt; Andreev, Alexander; Konoplev, Ivan

    2017-03-01

    A novel method for generating GigaGauss solenoidal fields in a laser-plasma bubble, using screw-shaped laser pulses, has been recently presented. Such magnetic fields enable fast synchrotron radiation cooling of the beam emittance of laser-plasma accelerated leptons. This recent finding opens a novel approach for design of laser-plasma FELs or colliders, where the acceleration stages are interleaved with laser-plasma emittance cooling stages. In this concept paper, we present an outline of what a staged plasma-acceleration FEL could look like, and discuss further studies needed to investigate the feasibility of the concept in detail.

  15. Dynamic Contrast-Enhanced Magnetic Resonance Imaging of Regional Nodal Metastasis in Nasopharyngeal Carcinoma: Correlation with Nodal Staging

    Directory of Open Access Journals (Sweden)

    Bingsheng Huang

    2017-01-01

    Full Text Available Objective. To determine if the perfusion parameters by dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI of regional nodal metastasis are helpful in characterizing nodal status and to understand the relationship with those of primary tumor of nasopharyngeal carcinoma (NPC. Materials and Methods. Newly diagnosed patients imaged between August 2010 and January 2014 and who were found to have enlarged retropharyngeal/cervical lymph nodes suggestive of nodal disease were recruited. DCE-MRI was performed. Three quantitative parameters, Ktrans, ve, and kep, were calculated for the largest node in each patient. Kruskal-Wallis test was used to evaluate the difference in the parameters of the selected nodes of different N stages. Spearman’s correlation was used to evaluate the relationship between the DCE-MRI parameters in nodes and in primary tumors. Results. Twenty-six patients (7 females; 25~67 years old were enrolled. Ktrans was significantly different among the patients of N stages (N1, n=3; N2, n=17; N3, n=6, P=0.015. Median values (range for N1, N2, and N3 were 0.24 min−1 (0.17~0.26 min−1, 0.29 min−1 (0.17~0.46 min−1, and 0.46 min−1 (0.29~0.70 min−1, respectively. There was no significant correlation between the parameters in nodes and primary tumors. Conclusion. DCE-MRI may play a distinct role in characterizing the metastatic cervical lymph nodes of NPC.

  16. Effect of high-frequency repetitive transcranial magnetic stimulation on motor cortical excitability and sensory nerve conduction velocity in subacute-stage incomplete spinal cord injury patients.

    Science.gov (United States)

    Cha, Hyun Gyu; Ji, Sang-Goo; Kim, Myoung-Kwon

    2016-07-01

    [Purpose] The aim of the present study was to determine whether repetitive transcranial magnetic stimulation can improve sensory recovery of the lower extremities in subacute-stage spinal cord injury patients. [Subjects and Methods] This study was conducted on 20 subjects with diagnosed paraplegia due to spinal cord injury. These 20 subjects were allocated to an experimental group of 10 subjects that underwent active repetitive transcranial magnetic stimulation or to a control group of 10 subjects that underwent sham repetitive transcranial magnetic stimulation. The SCI patients in the experimental group underwent active repetitive transcranial magnetic stimulation and conventional rehabilitation therapy, whereas the spinal cord injury patients in the control group underwent sham repetitive transcranial magnetic stimulation and conventional rehabilitation therapy. Participants in both groups received therapy five days per week for six-weeks. Latency, amplitude, and sensory nerve conduction velocity were assessed before and after the six week therapy period. [Results] A significant intergroup difference was observed for posttreatment velocity gains, but no significant intergroup difference was observed for amplitude or latency. [Conclusion] repetitive transcranial magnetic stimulation may be improve sensory recovery of the lower extremities in subacute-stage spinal cord injury patients.

  17. Research cardiac magnetic resonance imaging in end stage renal disease - incidence, significance and implications of unexpected incidental findings

    Energy Technology Data Exchange (ETDEWEB)

    Rutherford, Elaine; Weir-McCall, Jonathan R.; Houston, J.G.; Struthers, Allan D. [Ninewells Hospital, Division of Cardiovascular and Diabetes Medicine, Dundee (United Kingdom); Patel, Rajan K.; Jardine, Alan G.; Mark, Patrick B. [Institute of Cardiovascular and Medical Sciences, Glasgow (United Kingdom); Roditi, Giles [NHS Greater Glasgow and Clyde, Department of Radiology, Glasgow Royal Infirmary, Glasgow (United Kingdom)

    2017-01-15

    Left ventricular mass (LVM) at cardiac magnetic resonance imaging (CMR) is a frequent end point in clinical trials in nephrology. Trial participants with end stage renal disease (ESRD) may have a greater frequency of incidental findings (IF). We retrospectively investigated prevalence of IF in previous research CMR and reviewed their subsequent impact on participants. Between 2002 and 2006, 161 ESRD patients underwent CMR in a transplant assessment study. Images were used to assess LV mass and function. In the current study a radiologist reviewed the scans for IF. Review of patient records determined the subsequent clinical significance of IF. There were 150 IF in 95 study participants. Eighty-four (56 %) were new diagnoses. One hundred and two were non-cardiac. Fifteen were suspicious of malignancy. There was a clinically significant IF for 14.9 % of the participants. In six cases earlier identification of an IF may have improved quality of life or survival. Without radiology support clinically important IF may be missed on CMR. Patients undergoing CMR in trials should be counselled about the frequency and implications of IF. Patients with ESRD have a higher prevalence of IF than reported in other populations. Nephrology studies require mechanisms for radiologist reporting and strategies for dealing with IF. (orig.)

  18. Transcranial magnetic stimulation reveals two functionally distinct stages of motor cortex involvement during perception of emotional body language.

    Science.gov (United States)

    Borgomaneri, Sara; Gazzola, Valeria; Avenanti, Alessio

    2015-09-01

    Studies indicate that perceiving emotional body language recruits fronto-parietal regions involved in action execution. However, the nature of such motor activation is unclear. Using transcranial magnetic stimulation (TMS) we provide correlational and causative evidence of two distinct stages of motor cortex engagement during emotion perception. Participants observed pictures of body expressions and categorized them as happy, fearful or neutral while receiving TMS over the left or right motor cortex at 150 and 300 ms after picture onset. In the early phase (150 ms), we observed a reduction of excitability for happy and fearful emotional bodies that was specific to the right hemisphere and correlated with participants' disposition to feel personal distress. This 'orienting' inhibitory response to emotional bodies was also paralleled by a general drop in categorization accuracy when stimulating the right but not the left motor cortex. Conversely, at 300 ms, greater excitability for negative, positive and neutral movements was found in both hemispheres. This later motor facilitation marginally correlated with participants' tendency to assume the psychological perspectives of others and reflected simulation of the movement implied in the neutral and emotional body expressions. These findings highlight the motor system's involvement during perception of emotional bodies. They suggest that fast orienting reactions to emotional cues--reflecting neural processing necessary for visual perception--occur before motor features of the observed emotional expression are simulated in the motor system and that distinct empathic dispositions influence these two neural motor phenomena. Implications for theories of embodied simulation are discussed.

  19. Magnets

    International Nuclear Information System (INIS)

    Young, I.R.

    1984-01-01

    A magnet pole piece for an NMR imaging magnet is made of a plurality of magnetic wires with one end of each wire held in a non-magnetic spacer, the other ends of the wires being brought to a pinch, and connected to a magnetic core. The wires may be embedded in a synthetic resin and the magnetisation and uniformity thereof can be varied by adjusting the density of the wires at the spacer which forms the pole piece. (author)

  20. Study of Plasma Liner Driven Magnetized Target Fusion Via Advanced Simulations

    Energy Technology Data Exchange (ETDEWEB)

    Samulyak, Roman V. [State Univ. of New York (SUNY), Stony Brook, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States); Parks, Paul [General Atomics, San Diego, CA (United States)

    2013-08-31

    The feasibility of the plasma liner driven Magnetized Target Fusion (MTF) via terascale numerical simulations will be assessed. In the MTF concept, a plasma liner, formed by merging of a number (60 or more) of radial, highly supersonic plasma jets, implodes on the target in the form of two compact plasma toroids, and compresses it to conditions of the fusion ignition. By avoiding major difficulties associated with both the traditional laser driven inertial confinement fusion and solid liner driven MTF, the plasma liner driven MTF potentially provides a low-cost and fast R&D path towards the demonstration of practical fusion energy. High fidelity numerical simulations of full nonlinear models associated with the plasma liner MTF using state-of-art numerical algorithms and terascale computing are necessary in order to resolve uncertainties and provide guidance for future experiments. At Stony Brook University, we have developed unique computational capabilities that ideally suite the MTF problem. The FronTier code, developed in collaboration with BNL and LANL under DOE funding including SciDAC for the simulation of 3D multi-material hydro and MHD flows, has beenbenchmarked and used for fundamental and engineering problems in energy science applications. We have performed 3D simulations of converging supersonic plasma jets, their merger and the formation of the plasma liner, and a study of the corresponding oblique shock problem. We have studied the implosion of the plasma liner on the magnetized plasma target by resolving Rayleigh-Taylor instabilities in 2D and 3D and other relevant physics and estimate thermodynamic conditions of the target at the moment of maximum compression and the hydrodynamic efficiency of the method.

  1. Mapping the extent of disease by multislice computed tomography, magnetic resonance imaging and sentinel node evaluation in stage I and II cervical carcinoma

    Directory of Open Access Journals (Sweden)

    Rajaram S

    2010-01-01

    Full Text Available Aims: (1 To map the extent of disease in women with stage I and II carcinoma cervix by multislice spiral computed tomography (CT, magnetic resonance imaging (MRI and sentinel nodes. (2 To assess accuracy of each modality individually and in conjunction with FIGO clinical staging. Design and Setting: Prospective, single-blind study. Departments of Obstetrics and Gynaecology, Radiodiagnosis, and Pathology, UCMS and GTBH and Division of Radiological Imaging and Bioinformatics, INMAS, Delhi. Material and Method: The study was conducted on 25 women with cervical cancer FIGO stage I and II. Each woman underwent clinical staging, multislice spiral CT and MRI which was compared to the gold-standard histopathology/cytology. The overall accuracy of each modality and improvement of clinical staging by CT/MRI were noted. Sentinel nodes were evaluated by intracervical Patent Blue V dye injection. Statistical Analysis: Sensitivity, specificity, positive and negative predictive values were calculated by 2Χ2 contingency tables. Results: The accuracy of staging by FIGO, CT and MRI was 68%, 52% and 80%, respectively. MRI and CT improved the overall accuracy of FIGO staging to 96% and 80%, respectively. Sentinel nodes were identified in 89% of patients with 91% accuracy. Conclusion: MRI emerges as the most valuable stand-alone modality improving accuracy of FIGO staging to 96%. Sentinel lymph-node evaluation appears promising in evaluating spread beyond cervix.

  2. Dynamics of Plasma Jets and Bubbles Launched into a Transverse Background Magnetic Field

    Science.gov (United States)

    Zhang, Yue

    2017-10-01

    A coaxial magnetized plasma gun has been utilized to launch both plasma jets (open B-field) and plasma bubbles (closed B-field) into a transverse background magnetic field in the HelCat (Helicon-Cathode) linear device at the University of New Mexico. These situations may have bearing on fusion plasmas (e.g. plasma injection for tokamak fueling, ELM pacing, or disruption mitigation) and astrophysical settings (e.g. astrophysical jet stability, coronal mass ejections, etc.). The magnetic Reynolds number of the gun plasma is 100 , so that magnetic advection dominates over magnetic diffusion. The gun plasma ram pressure, ρjetVjet2 >B02 / 2μ0 , the background magnetic pressure, so that the jet or bubble can easily penetrate the background B-field, B0. When the gun axial B-field is weak compared to the gun azimuthal field, a current-driven jet is formed with a global helical magnetic configuration. Applying the transverse background magnetic field, it is observed that the n = 1 kink mode is stabilized, while magnetic probe measurements show contrarily that the safety factor q(a) drops below unity. At the same time, a sheared axial jet velocity is measured. We conclude that the tension force arising from increasing curvature of the background magnetic field induces the measured sheared flow gradient above the theoretical kink-stabilization threshold, resulting in the emergent kink stabilization of the injected plasma jet. In the case of injected bubbles, spheromak-like plasma formation is verified. However, when the spheromak plasma propagates into the transverse background magnetic field, the typical self-closed global symmetry magnetic configuration does not hold any more. In the region where the bubble toroidal field opposed the background B-field, the magneto-Rayleigh-Taylor (MRT) instability has been observed. Details of the experiment setup, diagnostics, experimental results and theoretical analysis will be presented. Supported by the National Science Foundation

  3. Proposal for a magnetic resonance imaging protocol for the detection of epileptogenic lesions at early outpatient stages.

    Science.gov (United States)

    Wellmer, Jörg; Quesada, Carlos M; Rothe, Lars; Elger, Christian E; Bien, Christian G; Urbach, Horst

    2013-11-01

    Magnetic resonance imaging (MRI) is a key technology in the presurgical evaluation of patients with epilepsy. Already at early outpatient stages it can contribute to the identification of patients who are, in the case of pharmacoresistance, good candidates for epilepsy surgery. Yet, "standard head" MRI examinations often fail to displaying therapeutically relevant epileptogenic lesions. The purpose of this study is to identify an epilepsy-specific MRI protocol, which is likewise sensitive for even small epileptogenic lesions and economical enough to be applied outside specialized epilepsy centers. Based on a large European presurgical epilepsy program comprising 2,740 patients we identified the spectrum of common epileptogenic lesions and determine the set of MRI sequences that are required for their reliable detection. Relying on a series of small, therapeutically particularly relevant lesions we determined the required slices thickness, slice angulations, and orientations for an epilepsy-specific MRI protocol. Indispensable for early outpatient epilepsy specific MRI are fluid attenuated inversion recovery (FLAIR), T(2) -weighted, T(1) -weighted, and hemosiderin/calcification-sensitive sequences. Slice thickness for T(2) and FLAIR must not exceed 3 mm. The T(1) image should be acquired in three-dimensional technique at 1 mm isotropic voxels size. For T(2) and FLAIR, at least two slice orientations each must be demanded in hippocampal angulation. We suggest no adaption to a clinical focus hypothesis. The resulting "essential 6" sequence protocol allows the detection of virtually all common epileptogenic lesion entities. The creation of a broadly accepted and abundantly applied MRI protocol for epilepsy outpatients can contribute to improved and earlier identification of potential candidates for epilepsy surgery. Our systematic analysis of MRI requirements for the detection of epileptogenic lesions can serve as basis for protocol negotiations between epileptologists

  4. Interobserver Agreement in Diagnosing Early-Stage Kienböck Disease on Radiographs and Magnetic Resonance Imaging.

    Science.gov (United States)

    van Leeuwen, Wouter F; Janssen, Stein J; Guitton, Thierry G; Chen, Neal; Ring, David

    2017-11-01

    The appearance of early Kienböck disease on radiographs and magnetic resonance imaging (MRI) may be difficult to distinguish from other conditions that affect the lunate. We aimed to assess the interobserver agreement in the diagnosis of early Kienböck disease when evaluated on different imaging modalities. Forty-three hand surgeon members of the Science of Variation Group were randomized to evaluate radiographs and 35 hand surgeons to evaluate radiographs and MRI scans of 26 patients for the presence of Kienböck disease, the lunate type, and the ulnar variance. We used Fleiss' kappa analysis to assess the interobserver agreement for categorical variables and compared the κ values between the 2 groups. We found that agreement on the diagnosis of early Kienböck disease was fair (κ, 0.36) among observers who evaluated radiographs alone and moderate (κ, 0.58) among observers who evaluated MRI scans in addition to radiographs, and that the difference in κ values was not statistically significant ( P = .057). Agreement did not differ between observers based on imaging modality with regard to the assessment of the lunate type ( P = .75) and ulnar variance ( P = .15). We found, with the numbers evaluated, a notable but nonsignificant difference in agreement in favor of observers who evaluated MRI scans in addition to radiographs compared with radiographs alone. Surgeons should be aware that the diagnosis of Kienböck disease in the precollapse stages is not well defined, as evidenced by the substantial interobserver variability.

  5. Rectal cancer staging: focus on the prognostic significance of the findings described by high-resolution magnetic resonance imaging

    Science.gov (United States)

    2013-01-01

    Abstract High-resolution (HR) magnetic resonance imaging (MRI) has become an indispensable tool for multidisciplinary teams (MDTs) addressing rectal cancer. It provides anatomic information for surgical planning and allows patients to be stratified into different groups according to the risk of local and distant recurrence. One of the objectives of the MDT is the preoperative identification of high-risk patients who will benefit from neoadjuvant treatment. For this reason, the correct evaluation of the circumferential resection margin (CRM), the depth of tumor spread beyond the muscularis propria, extramural vascular invasion and nodal status is of the utmost importance. Low rectal tumors represent a special challenge for the MDT, because decisions seek a balance between oncologic safety, in the pursuit of free resection margins, and the patient’s quality of life, in order to preserve sphincter function. At present, the exchange of information between the different specialties involved in dealing with patients with rectal cancer can rank the contribution of colleagues, auditing their work and incorporating knowledge that will lead to a better understanding of the pathology. Thus, beyond the anatomic description of the images, the radiologist’s role in the MDT makes it necessary to know the prognostic value of the findings that we describe, in terms of recurrence and survival, because these findings affect decision making and, therefore, the patients’ life. In this review, the usefulness of HR MRI in the initial staging of rectal cancer and in the evaluation of neoadjuvant treatment, with a focus on the prognostic value of the findings, is described as well as the contribution of HR MRI in assessing patients with suspected or confirmed recurrence of rectal cancer. PMID:23876415

  6. Classification and localization of early-stage Alzheimer's disease in magnetic resonance images using a patch-based classifier ensemble

    International Nuclear Information System (INIS)

    Simoes, Rita; Slump, Cornelis H.; Cappellen van Walsum, Anne-Marie van

    2014-01-01

    Classification methods have been proposed to detect Alzheimer's disease (AD) using magnetic resonance images. Most rely on features such as the shape/volume of brain structures that need to be defined a priori. In this work, we propose a method that does not require either the segmentation of specific brain regions or the nonlinear alignment to a template. Besides classification, we also analyze which brain regions are discriminative between a group of normal controls and a group of AD patients. We perform 3D texture analysis using Local Binary Patterns computed at local image patches in the whole brain, combined in a classifier ensemble. We evaluate our method in a publicly available database including very mild-to-mild AD subjects and healthy elderly controls. For the subject cohort including only mild AD subjects, the best results are obtained using a combination of large (30 x 30 x 30 and 40 x 40 x 40 voxels) patches. A spatial analysis on the best performing patches shows that these are located in the medial-temporal lobe and in the periventricular regions. When very mild AD subjects are included in the dataset, the small (10 x 10 x 10 voxels) patches perform best, with the most discriminative ones being located near the left hippocampus. We show that our method is able not only to perform accurate classification, but also to localize discriminative brain regions, which are in accordance with the medical literature. This is achieved without the need to segment-specific brain structures and without performing nonlinear registration to a template, indicating that the method may be suitable for a clinical implementation that can help to diagnose AD at an earlier stage.

  7. Magnetic entropy changes at early stages of nanocrystallization in amorphous Fe{sub 90}Zr{sub 7}B{sub 3} ribbons

    Energy Technology Data Exchange (ETDEWEB)

    Swierczek, J., E-mail: swiercz@wip.pcz.pl [Institute of Physics, Czestochowa University of Technology, al. Armii Krajowej 19, 42-200 Czestochowa (Poland); Mydlarz, T. [International Laboratory of High Magnetic Fields and Low Temperatures, ul.Gajowicka 95, 53-421 Wroclaw (Poland)

    2011-09-22

    Highlights: > Magnetic entropy changes in partially crystallized Fe{sub 90}Zr{sub 7}B{sub 3} alloy. > Microstructure by transmission electron microscopy and Moessbauer spectrometry. > Superparamagnetic {alpha}-Fe particles in amorphous matrix. > Curie temperature of matrix increases on annealing. > Maximum entropy changes remain almost unchanged. - Abstract: Microstructure, revealed by transmission electron microscopy and conventional Moessbauer spectroscopy, magnetization versus magnetizing field induction and temperature and isothermal magnetic entropy changes in the as-quenched and subjected to annealing at T{sub a1} = 723 K for 2 or 3 h and at T{sub a2} = 743 K for 2.5 h of Fe{sub 90}Zr{sub 7}B{sub 3} amorphous alloy are studied. In the as-quenched state the medium range ordered regions are observed. The annealing at T{sub a1} leads to early stages of crystallization and nanograins with different diameter embedded in amorphous matrix are formed. At the Curie point of the amorphous phase they are magnetically decoupled and behave like superparamagnetic particles. The Curie point of the residual amorphous phase shifts towards higher temperature as compared to the as-quenched state due to the Invar like effect. The peak of the isothermal magnetic entropy changes appears at the Curie temperature of the main amorphous phase. Their values at the maximum applied field of 0.75 T equals to 0.32 J/kg K{sup -1} in the as-quenched alloy and remain almost unchanged after early stages of nanocrystallization. After the annealing at T{sub a2} the peak of the entropy changes distinctly decreases. Such behavior is ascribed to the biphasic character of the sample. The main amorphous phase and ordered one, which in some circumstances can be treated as an assembly of superparamagnetic particles, contribute to the total magnetic entropy changes.

  8. Laser light and magnetic field stimulation effect on biochemical, enzymes activities and chlorophyll contents in soybean seeds and seedlings during early growth stages.

    Science.gov (United States)

    Asghar, Tehseen; Jamil, Yasir; Iqbal, Munawar; Zia-Ul-Haq; Abbas, Mazhar

    2016-12-01

    Laser and magnetic field bio-stimulation attracted the keen interest of scientific community in view of their potential to enhance seed germination, seedling growth, physiological, biochemical and yield attributes of plants, cereal crops and vegetables. Present study was conducted to appraise the laser and magnetic field pre-sowing seed treatment effects on soybean sugar, protein, nitrogen, hydrogen peroxide (H 2 O 2 ) ascorbic acid (AsA), proline, phenolic and malondialdehyde (MDA) along with chlorophyll contents (Chl "a" "b" and total chlorophyll contents). Specific activities of enzymes such as protease (PRT), amylase (AMY), catalyst (CAT), superoxide dismutase (SOD) and peroxides (POD) were also assayed. The specific activity of enzymes (during germination and early growth), biochemical and chlorophyll contents were enhanced significantly under the effect of both laser and magnetic pre-sowing treatments. Magnetic field treatment effect was slightly higher than laser treatment except PRT, AMY and ascorbic acid contents. However, both treatments (laser and magnetic field) effects were significantly higher versus control (un-treated seeds). Results revealed that laser and magnetic field pre-sowing seed treatments have potential to enhance soybean biological moieties, chlorophyll contents and metabolically important enzymes (degrade stored food and scavenge reactive oxygen species). Future study should be focused on growth characteristics at later stages and yield attributes. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Experiments on helical modes in magnetized thin foil-plasmas

    Science.gov (United States)

    Yager-Elorriaga, David

    2017-10-01

    This paper gives an in-depth experimental study of helical features on magnetized, ultrathin foil-plasmas driven by the 1-MA linear transformer driver at University of Michigan. Three types of cylindrical liner loads were designed to produce: (a) pure magneto-hydrodynamic (MHD) modes (defined as being void of the acceleration-driven magneto-Rayleigh-Taylor instability, MRT) using a non-imploding geometry, (b) pure kink modes using a non-imploding, kink-seeded geometry, and (c) MRT-MHD coupled modes in an unseeded, imploding geometry. For each configuration, we applied relatively small axial magnetic fields of Bz = 0.2-2.0 T (compared to peak azimuthal fields of 30-40 T). The resulting liner-plasmas and instabilities were imaged using 12-frame laser shadowgraphy and visible self-emission on a fast framing camera. The azimuthal mode number was carefully identified with a tracking algorithm of self-emission minima. Our experiments show that the helical structures are a manifestation of discrete eigenmodes. The pitch angle of the helix is simply m / kR , from implosion to explosion, where m, k, and R are the azimuthal mode number, axial wavenumber, and radius of the helical instability. Thus, the pitch angle increases (decreases) during implosion (explosion) as R becomes smaller (larger). We found that there are one, or at most two, discrete helical modes that arise for magnetized liners, with no apparent threshold on the applied Bz for the appearance of helical modes; increasing the axial magnetic field from zero to 0.5 T changes the relative weight between the m = 0 and m = 1 modes. Further increasing the applied axial magnetic fields yield higher m modes. Finally, the seeded kink instability overwhelms the intrinsic instability modes of the plasma. These results are corroborated with our analytic theory on the effects of radial acceleration on the classical sausage, kink, and higher m modes. Work supported by US DOE award DE-SC0012328, Sandia National Laboratories

  10. A two-stage evolution of Visakhapatnam-Paradip Shelf, east coast of India, from magnetic studies

    Digital Repository Service at National Institute of Oceanography (India)

    Subrahmanyam, A.S.; Murthy, K.S.R.; Rao, T.C.S.; Rao, M.M.M.; Lakshminarayana, S.; Venkateswarlu, K.

    A detailed analysis of bathymetry and magnetic data of Visakhapatnam-Paradip shelf, east coast of India revealed three major structural lineaments over the shelf/slope of the area. Models derived from the anomalies associated with the trends...

  11. MAGNET

    CERN Multimedia

    by B. Curé

    2011-01-01

    The magnet operation was very satisfactory till the technical stop at the end of the year 2010. The field was ramped down on 5th December 2010, following the successful regeneration test of the turbine filters at full field on 3rd December 2010. This will limit in the future the quantity of magnet cycles, as it is no longer necessary to ramp down the magnet for this type of intervention. This is made possible by the use of the spare liquid Helium volume to cool the magnet while turbines 1 and 2 are stopped, leaving only the third turbine in operation. This obviously requires full availability of the operators to supervise the operation, as it is not automated. The cryogenics was stopped on 6th December 2010 and the magnet was left without cooling until 18th January 2011, when the cryoplant operation resumed. The magnet temperature reached 93 K. The maintenance of the vacuum pumping was done immediately after the magnet stop, when the magnet was still at very low temperature. Only the vacuum pumping of the ma...

  12. General Relativistic Magnetohydrodynamic Simulations of Magnetically Choked Accretion Flows around Black Holes

    Energy Technology Data Exchange (ETDEWEB)

    McKinney, Jonathan C.; Tchekhovskoy, Alexander; Blandford, Roger D.

    2012-04-26

    Black hole (BH) accretion flows and jets are qualitatively affected by the presence of ordered magnetic fields. We study fully three-dimensional global general relativistic magnetohydrodynamic (MHD) simulations of radially extended and thick (height H to cylindrical radius R ratio of |H/R| {approx} 0.2-1) accretion flows around BHs with various dimensionless spins (a/M, with BH mass M) and with initially toroidally-dominated ({phi}-directed) and poloidally-dominated (R-z directed) magnetic fields. Firstly, for toroidal field models and BHs with high enough |a/M|, coherent large-scale (i.e. >> H) dipolar poloidal magnetic flux patches emerge, thread the BH, and generate transient relativistic jets. Secondly, for poloidal field models, poloidal magnetic flux readily accretes through the disk from large radii and builds-up to a natural saturation point near the BH. While models with |H/R| {approx} 1 and |a/M| {le} 0.5 do not launch jets due to quenching by mass infall, for sufficiently high |a/M| or low |H/R| the polar magnetic field compresses the inflow into a geometrically thin highly non-axisymmetric 'magnetically choked accretion flow' (MCAF) within which the standard linear magneto-rotational instability is suppressed. The condition of a highly-magnetized state over most of the horizon is optimal for the Blandford-Znajek mechanism that generates persistent relativistic jets with and 100% efficiency for |a/M| {approx}> 0.9. A magnetic Rayleigh-Taylor and Kelvin-Helmholtz unstable magnetospheric interface forms between the compressed inflow and bulging jet magnetosphere, which drives a new jet-disk oscillation (JDO) type of quasi-periodic oscillation (QPO) mechanism. The high-frequency QPO has spherical harmonic |m| = 1 mode period of {tau} {approx} 70GM/c{sup 3} for a/M {approx} 0.9 with coherence quality factors Q {approx}> 10. Overall, our models are qualitatively distinct from most prior MHD simulations (typically, |H/R| << 1 and poloidal flux is

  13. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      Following the unexpected magnet stops last August due to sequences of unfortunate events on the services and cryogenics [see CMS internal report], a few more events and initiatives again disrupted the magnet operation. All the magnet parameters stayed at their nominal values during this period without any fault or alarm on the magnet control and safety systems. The magnet was stopped for the September technical stop to allow interventions in the experimental cavern on the detector services. On 1 October, to prepare the transfer of the liquid nitrogen tank on its new location, several control cables had to be removed. One cable was cut mistakenly, causing a digital input card to switch off, resulting in a cold-box (CB) stop. This tank is used for the pre-cooling of the magnet from room temperature down to 80 K, and for this reason it is controlled through the cryogenics control system. Since the connection of the CB was only allowed for a field below 2 T to avoid the risk of triggering a fast d...

  14. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet was energised at the beginning of March 2012 at a low current to check all the MSS safety chains. Then the magnet was ramped up to 3.8 T on 6 March 2012. Unfortunately two days later an unintentional switch OFF of the power converter caused a slow dump. This was due to a misunderstanding of the CCC (CERN Control Centre) concerning the procedure to apply for the CMS converter control according to the beam-mode status at that time. Following this event, the third one since 2009, a discussion was initiated to define possible improvement, not only on software and procedures in the CCC, but also to evaluate the possibility to upgrade the CMS hardware to prevent such discharge from occurring because of incorrect procedure implementations. The magnet operation itself was smooth, and no power cuts took place. As a result, the number of magnetic cycles was reduced to the minimum, with only two full magnetic cycles from 0 T to 3.8 T. Nevertheless the magnet suffered four stops of the cryogeni...

  15. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    Operation of the magnet has gone quite smoothly during the first half of this year. The magnet has been at 4.5K for the full period since January. There was an unplanned short stop due to the CERN-wide power outage on May 28th, which caused a slow dump of the magnet. Since this occurred just before a planned technical stop of the LHC, during which access in the experimental cavern was authorized, it was decided to leave the magnet OFF until 2nd June, when magnet was ramped up again to 3.8T. The magnet system experienced a fault also resulting in a slow dump on April 14th. This was triggered by a thermostat on a filter choke in the 20kA DC power converter. The threshold of this thermostat is 65°C. However, no variation in the water-cooling flow rate or temperature was observed. Vibration may have been the root cause of the fault. All the thermostats have been checked, together with the cables, connectors and the read out card. The tightening of the inductance fixations has also been checked. More tem...

  16. Effects of recombinant human erythropoietin on the haemopoietic bone marrow monitored by magnetic resonance spectroscopy in patients with end-stage renal disease

    DEFF Research Database (Denmark)

    Jensen, K E; Stenver, D; Jensen, M

    1990-01-01

    Volume selective magnetic resonance (MR) proton spectroscopy was used to investigate changes in the haemopoietic bone marrow in patients with end-stage renal disease undergoing treatment with recombinant human erythropoietin (rHuEPO). Significant changes could be detected in the spectra 14 days...... change in the spectrum four days after treatment began, indicating that MR spectroscopy may detect early changes in the cellular composition of the bone marrow. This noninvasive method may be useful in evaluating treatment effects of recombinant human haemopoietic growth factors in the bone marrow...

  17. Analysis of Bone Mineral Density in Multiple Myeloma: A Comparison of Bone Mineral Density with Plain Radiography, Magnetic Resonance Imaging, and Clinical Staging

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji Na; Kwon, Soon Tae; Song, Ik Chan [Dept. of Chungnam National University Hospital, Daejeon (Korea, Republic of)

    2013-01-15

    To analyze the bone mineral density (BMD) in multiple myeloma (MM) and to compare BMD with plain radiography, MRI and clinical stage. We reviewed 59 patients with MM and an age- and sex-matched control group, with measured BMD. The L-spine and femoral neck (FN) BMD were measured by dual-energy X-ray absorptiometry. Lateral plain radiographs of the L-spine were graded as 3 stages using the modified Saville index. Four bone marrow patterns were classified on sagittal T1- and T2-weighted magnetic resonance images of the L-spine. BMD in the MM and control group were analyzed. BMD in MM was compared with the modified Saville index, bone marrow patterns on MRI, and clinical stages. In MM, spine BMD was reduced and the difference between spine and FN BMD was larger than the control group (p < 0.001). The modified Saville index was negatively correlated with spine T scores (p < 0.01). The spine BMD in normal marrow pattern on the MRI was the most reduced. There was no statistical correlation between BMD and clinical stage. In MM, spine BMD was significantly reduced and the difference between spine and FN BMD was larger than the control group. The modified Saville index was significantly correlated with spine BMD in MM.

  18. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

      The magnet was operated without any problem until the end of the LHC run in February 2013, apart from a CERN-wide power glitch on 10 January 2013 that affected the CMS refrigerator, causing a ramp down to 2 T in order to reconnect the coldbox. Another CERN-wide power glitch on 15 January 2013 didn’t affect the magnet subsystems, the cryoplant or the power converter. At the end of the magnet run, the reconnection of the coldbox at 2.5 T was tested. The process will be updated, in particular the parameters of some PID valve controllers. The helium flow of the current leads was reduced but only for a few seconds. The exercise will be repeated with the revised parameters to validate the automatic reconnection process of the coldbox. During LS1, the water-cooling services will be reduced and many interventions are planned on the electrical services. Therefore, the magnet cryogenics and subsystems will be stopped for several months, and the magnet cannot be kept cold. In order to avoid unc...

  19. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet was successfully operated at the end of the year 2009 despite some technical problems on the cryogenics. The magnet was ramped up to 3.8 T at the end of November until December 16th when the shutdown started. The magnet operation met a few unexpected stops. The field was reduced to 3.5 T for about 5 hours on December 3rd due to a faulty pressure sensor on the helium compressor. The following day the CERN CCC stopped unintentionally the power converters of the LHC and the experiments, triggering a ramp down that was stopped at 2.7 T. The magnet was back at 3.8 T about 6 hours after CCC sent the CERN-wide command. Three days later, a slow dump was triggered due to a stop of the pump feeding the power converter water-cooling circuit, during an intervention on the water-cooling plant done after several disturbances on the electrical distribution network. The magnet was back at 3.8 T in the evening the same day. On December 10th a break occurred in one turbine of the cold box producing the liquid ...

  20. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The CMS magnet has been running steadily and smoothly since the summer, with no detected flaw. The magnet instrumentation is entirely operational and all the parameters are at their nominal values. Three power cuts on the electrical network affected the magnet run in the past five months, with no impact on the data-taking as the accelerator was also affected at the same time. On 22nd June, a thunderstorm caused a power glitch on the service electrical network. The primary water cooling at Point 5 was stopped. Despite a quick restart of the water cooling, the inlet temperature of the demineralised water on the busbar cooling circuit increased by 5 °C, up to 23.3 °C. It was kept below the threshold of 27 °C by switching off other cooling circuits to avoid the trigger of a slow dump of the magnet. The cold box of the cryogenics also stopped. Part of the spare liquid helium volume was used to maintain the cooling of the magnet at 4.5 K. The operators of the cryogenics quickly restarted ...

  1. MAGNET

    CERN Multimedia

    B. Curé

    2012-01-01

      The magnet and its sub-systems were stopped at the beginning of the winter shutdown on 8th December 2011. The magnet was left without cooling during the cryogenics maintenance until 17th January 2012, when the cryoplant operation resumed. The magnet temperature reached 93 K. The vacuum pumping was maintained during this period. During this shutdown, the yearly maintenance was performed on the cryogenics, the vacuum pumps, the magnet control and safety systems, and the power converter and discharge lines. Several preventive actions led to the replacement of the electrovalve command coils, and the 20A DC power supplies of the magnet control system. The filters were cleaned on the demineralised water circuits. The oil of the diffusion pumps was changed. On the cryogenics, warm nitrogen at 343 K was circulated in the cold box to regenerate the filters and the heat exchangers. The coalescing filters have been replaced at the inlet of both the turbines and the lubricant trapping unit. The active cha...

  2. Eyes in the sky. Interactions between asymptotic giant branch star winds and the interstellar magnetic field

    Science.gov (United States)

    van Marle, A. J.; Cox, N. L. J.; Decin, L.

    2014-10-01

    Context. The extended circumstellar envelopes (CSEs) of evolved low-mass stars display a large variety of morphologies. Understanding the various mechanisms that give rise to these extended structures is important to trace their mass-loss history. Aims: Here, we aim to examine the role of the interstellar magnetic field in shaping the extended morphologies of slow dusty winds of asymptotic giant branch (AGB) stars in an effort to pin-point the origin of so-called eye shaped CSEs of three carbon-rich AGB stars. In addition, we seek to understand if this pre-planetary nebula (PN) shaping can be responsible for asymmetries observed in PNe. Methods: Hydrodynamical simulations are used to study the effect of typical interstellar magnetic fields on the free-expanding spherical stellar winds as they sweep up the local interstellar medium (ISM). Results: The simulations show that typical Galactic interstellar magnetic fields of 5 to 10 μG are sufficient to alter the spherical expanding shells of AGB stars to appear as the characteristic eye shape revealed by far-infrared observations. The typical sizes of the simulated eyes are in accordance with the observed physical sizes. However, the eye shapes are transient in nature. Depending on the stellar and interstellar conditions, they develop after 20 000 to 200 000 yrs and last for about 50 000 to 500 000 yrs, assuming that the star is at rest relative to the local interstellar medium. Once formed, the eye shape develops lateral outflows parallel to the magnetic field. The explosion of a PN in the centre of the eye-shaped dust shell gives rise to an asymmetrical nebula with prominent inward pointing Rayleigh-Taylor instabilities. Conclusions: Interstellar magnetic fields can clearly affect the shaping of wind-ISM interaction shells. The occurrence of the eyes is most strongly influenced by stellar space motion and ISM density. Observability of this transient phase is favoured for lines-of-sight perpendicular to the

  3. ''SMILE'': A Self Magnetically Insulated Transmission LinE adder for the 8-stage RADLAC II accelerator

    International Nuclear Information System (INIS)

    Mazarakis, M.G.; Poukey, J.W.; Shope, S.L.; Frost, C.A.; Turman, B.N.; Ramirez, J.J.; Prestwich, K.R.; Pankuch, P.J.

    1991-01-01

    The RADLAC II Self Magnetically Insulated Transmission LinE ''SMILE'' is a coaxial wave guide structure that is composed of two regions: (a) a 9.5-m voltage adder and (b) a 3-m long extension section. The adder section provides for the addition of the input voltages from the individual water-dielectric pulse forming line feeds. The extension section isolates the adder from the magnetically immersed foilless diode electron source load and efficiently transports the pulsed power out from the deionized water tank of the device. The SMILE modification of the RADLAC II accelerator enabled us to produce high quality beams of up to 14 MV, 100 kA. The design and the experimental evaluation of SMILE will be presented and compared with numerical simulation predictions. 12 refs., 9 figs., 1 tab

  4. SMILE'': A Self Magnetically Insulated Transmission LinE adder for the 8-stage RADLAC II accelerator

    Energy Technology Data Exchange (ETDEWEB)

    Mazarakis, M.G.; Poukey, J.W.; Shope, S.L.; Frost, C.A.; Turman, B.N.; Ramirez, J.J.; Prestwich, K.R. (Sandia National Labs., Albuquerque, NM (USA)); Pankuch, P.J. (EG and G Energy Measurements Group, Inc., Albuquerque, NM (USA). Special Projects)

    1991-01-01

    The RADLAC II Self Magnetically Insulated Transmission LinE SMILE'' is a coaxial wave guide structure that is composed of two regions: (a) a 9.5-m voltage adder and (b) a 3-m long extension section. The adder section provides for the addition of the input voltages from the individual water-dielectric pulse forming line feeds. The extension section isolates the adder from the magnetically immersed foilless diode electron source load and efficiently transports the pulsed power out from the deionized water tank of the device. The SMILE modification of the RADLAC II accelerator enabled us to produce high quality beams of up to 14 MV, 100 kA. The design and the experimental evaluation of SMILE will be presented and compared with numerical simulation predictions. 12 refs., 9 figs., 1 tab.

  5. MAGNET

    CERN Multimedia

    B. Curé

    2011-01-01

    The magnet ran smoothly in the last few months until a fast dump occurred on 9th May 2011. Fortunately, this occurred in the afternoon of the first day of the technical stop. The fast dump was due to a valve position controller that caused the sudden closure of a valve. This valve is used to regulate the helium flow on one of the two current leads, which electrically connects the coil at 4.5 K to the busbars at room temperature. With no helium flow on the lead, the voltage drop and the temperatures across the leads increase up to the defined thresholds, triggering a fast dump through the Magnet Safety System (MSS). The automatic reaction triggered by the MSS worked properly. The helium release was limited as the pressure rise was just at the limit of the safety valve opening pressure. The average temperature of the magnet reached 72 K. It took four days to recover the temperature and refill the helium volumes. The faulty valve controller was replaced by a spare one before the magnet ramp-up resumed....

  6. Prediction of pathologic staging with magnetic resonance imaging after preoperative chemoradiotherapy in rectal cancer: pooled analysis of KROG 10-01 and 11-02.

    Science.gov (United States)

    Lee, Jong Hoon; Jang, Hong Seok; Kim, Jun-Gi; Lee, Myung Ah; Kim, Dae Yong; Kim, Tae Hyun; Oh, Jae Hwan; Park, Sung Chan; Kim, Sun Young; Baek, Ji Yeon; Park, Hee Chul; Kim, Hee Cheol; Nam, Taek-Keun; Chie, Eui Kyu; Jung, Ji-Han; Oh, Seong Taek

    2014-10-01

    The reported overall accuracy of MRI in predicting the pathologic stage of nonirradiated rectal cancer is high. However, the role of MRI in restaging rectal tumors after neoadjuvant CRT is contentious. Thus, we evaluate the accuracy of restaging magnetic resonance imaging (MRI) for rectal cancer patients who receive preoperative chemoradiotherapy (CRT). We analyzed 150 patients with locally advanced rectal cancer (T3-4N0-2) who had received preoperative CRT. Pre-CRT MRI was performed for local tumor and nodal staging. All patients underwent restaging MRI followed by total mesorectal excision after the end of radiotherapy. The primary endpoint of the present study was to estimate the accuracy of post-CRT MRI as compared with pathologic staging. Pathologic T classification matched the post-CRT MRI findings in 97 (64.7%) of 150 patients. 36 (24.0%) of 150 patients were overstaged in T classification, and the concordance degree was moderate (k=0.33, prectal cancer patients who received preoperative CRT. The diagnostic accuracy of restaging MRI is relatively high in rectal cancer patients who achieved clinical downstaging after CRT. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

  7. The Use of Endoscopic Ultrasonography and Other Imaging Modalities in the Preoperative Staging of Rectal Villous Tumours: A Case of Overstaging by Magnetic Resonance Imaging

    Directory of Open Access Journals (Sweden)

    Michelle Buresi

    2009-01-01

    Full Text Available A case of a 60-year-old man with recurrent rectal villous adenoma is described. Preoperative staging with endoscopic ultrasound (EUS and magnetic resonance imaging (MRI revealed very discordant results. EUS showed a tumour present in the mucosa with no submucosal invasion, while MRI revealed invasion of the muscularis propria consistent with an invasive stage T2 carcinoma. Based on the MRI findings, the patient underwent a low anterior resection of the tumour. The surgical pathology specimen revealed a villous adenoma with low-grade dysplasia but no carcinoma and no extension into the muscularis propria. The present case highlights the uncertainty that currently exists as to which imaging modality provides the greatest accuracy in the staging of rectal cancer and in guiding the type of surgical procedure performed. Two recent meta-analyses and a systematic review of the literature point to EUS as the imaging modality of choice for determining muscularis propria and perirectal tissue invasion, as well as nodal involvement.

  8. Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields

    Science.gov (United States)

    Pogorelov, N. V.; Fichtner, H.; Czechowski, A.; Lazarian, A.; Lembege, B.; le Roux, J. A.; Potgieter, M. S.; Scherer, K.; Stone, E. C.; Strauss, R. D.; Wiengarten, T.; Wurz, P.; Zank, G. P.; Zhang, M.

    2017-10-01

    This paper summarizes the results obtained by the team "Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields" supported by the International Space Science Institute (ISSI) in Bern, Switzerland. We focus on the physical processes occurring in the outer heliosphere, especially at its boundary called the heliopause, and in the local interstellar medium. The importance of magnetic field, charge exchange between neutral atoms and ions, and solar cycle on the heliopause topology and observed heliocentric distances to different heliospheric discontinuities are discussed. It is shown that time-dependent, data-driven boundary conditions are necessary to describe the heliospheric asymmetries detected by the Voyager spacecraft. We also discuss the structure of the heliopause, especially due to its instability and magnetic reconnection. It is demonstrated that the Rayleigh-Taylor instability of the nose of the heliopause creates consecutive layers of the interstellar and heliospheric plasma which are magnetically connected to different sources. This may be a possible explanation of abrupt changes in the galactic and anomalous cosmic ray fluxes observed by Voyager 1 when it was crossing the heliopause structure for a period of about one month in the summer of 2012. This paper also discusses the plausibility of fitting simulation results to a number of observational data sets obtained by in situ and remote measurements. The distribution of magnetic field in the vicinity of the heliopause is discussed in the context of Voyager measurements. It is argued that a classical heliospheric current sheet formed due to the Sun's rotation is not observed by in situ measurements and should not be expected to exist in numerical simulations extending to the boundary of the heliosphere. Furthermore, we discuss the transport of energetic particles in the inner and outer heliosheath, concentrating on the anisotropic spatial

  9. MAGNET

    CERN Multimedia

    Benoit Curé

    2010-01-01

    The magnet worked very well at 3.8 T as expected, despite a technical issue that manifested twice in the cryogenics since June. All the other magnet sub-systems worked without flaw. The issue in the cryogenics was with the cold box: it could be observed that the cold box was getting progressively blocked, due to some residual humidity and air accumulating in the first thermal exchanger and in the adsorber at 65 K. This was later confirmed by the analysis during the regeneration phases. An increase in the temperature difference between the helium inlet and outlet across the heat exchanger and a pressure drop increase on the filter of the adsorber were observed. The consequence was a reduction of the helium flow, first compensated by the automatic opening of the regulation valves. But once they were fully opened, the flow and refrigeration power reduced as a consequence. In such a situation, the liquid helium level in the helium Dewar decreased, eventually causing a ramp down of the magnet current and a field...

  10. MAGNET

    CERN Multimedia

    B. Curé

    MAGNET During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bough...

  11. MAGNET

    CERN Multimedia

    B. Curé

    2013-01-01

    The magnet is fully stopped and at room temperature. The maintenance works and consolidation activities on the magnet sub-systems are progressing. To consolidate the cryogenic installation, two redundant helium compressors will be installed as ‘hot spares’, to avoid the risk of a magnet downtime in case of a major failure of a compressor unit during operation. The screw compressors, their motors, the mechanical couplings and the concrete blocks are already available and stored at P5. The metallic structure used to access the existing compressors in SH5 will be modified to allow the installation of the two redundant ones. The plan is to finish the installation and commissioning of the hot spare compressors before the summer 2014. In the meantime, a bypass on the high-pressure helium piping will be installed for the connection of a helium drier unit later during the Long Shutdown 1, keeping this installation out of the schedule critical path. A proposal is now being prepared for the con...

  12. MAGNET

    CERN Multimedia

    Benoit Curé.

    The magnet operation restarted end of June this year. Quick routine checks of the magnet sub-systems were performed at low current before starting the ramps up to higher field. It appeared clearly that the end of the field ramp down to zero was too long to be compatible with the detector commissioning and operations plans. It was decided to perform an upgrade to keep the ramp down from 3.8T to zero within 4 hours. On July 10th, when a field of 1.5T was reached, small movements were observed in the forward region support table and it was decided to fix this problem before going to higher field. At the end of July the ramps could be resumed. On July 28th, the field was at 3.8T and the summer CRAFT exercise could start. This run in August went smoothly until a general CERN wide power cut took place on August 3rd, due to an insulation fault on the high voltage network outside point 5. It affected the magnet powering electrical circuit, as it caused the opening of the main circuit breakers, resulting in a fast du...

  13. Clinical importance of second-opinion interpretations by radiologists specializing in gynecologic oncology at a tertiary cancer center: magnetic resonance imaging for endometrial cancer staging

    Directory of Open Access Journals (Sweden)

    Inês Alves

    2018-01-01

    Full Text Available Abstract Objective: To determine whether there are substantive differences between the initial interpretations of magnetic resonance imaging (MRI scans acquired at outside facilities and the second-opinion interpretations of radiologists specializing in gynecologic oncology at a tertiary cancer center, among patients referred for endometrial cancer staging. Materials and Methods: This was a retrospective, comparative analysis of 153 initial and second-opinion MRI reports for endometrial cancer staging officially submitted for review by radiologists specializing in gynecologic oncology. For each case, the relationship between the initial and second-opinion reports, regarding the suggested diagnosis and the clinically relevant MRI findings reported, was categorized as "agreement" or "disagreement". Histopathology was used in order to establish the definitive diagnosis. Results: Disagreement was found in 58 (37.9% of the 153 cases. Second-opinion interpretations reported findings that affected the preoperative cancer staging and could have led to a change in treatment in 38 cases (24.8%; that did not affect the preoperative staging but provided information that was more accurate in 8 (5.2%; and that suggested a new cancer diagnosis in 12 (7.8%. In 37 cases (24.2%, there was a potential for changes in patient care. Among the 58 cases of disagreement, a definitive (histopathological diagnosis was made in 41 (70.7%. In 31 (75.6% of those 41 cases, the second-opinion report was more accurate than was the initial report. Conclusion: Discordant interpretations of MRI examinations, which can have a substantial effect on the clinical management of patients, appear to be common.

  14. MAGNET

    CERN Multimedia

    Benoit Curé

    The magnet subsystems resumed operation early this spring. The vacuum pumping was restarted mid March, and the cryogenic power plant was restarted on March 30th. Three and a half weeks later, the magnet was at 4.5 K. The vacuum pumping system is performing well. One of the newly installed vacuum gauges had to be replaced at the end of the cool-down phase, as the values indicated were not coherent with the other pressure measurements. The correction had to be implemented quickly to be sure no helium leak could be at the origin of this anomaly. The pressure measurements have been stable and coherent since the change. The cryogenics worked well, and the cool-down went quite smoothly, without any particular difficulty. The automated start of the turbines had to be fine-tuned to get a smooth transition, as it was observed that the cooling power delivered by the turbines was slightly higher than needed, causing the cold box to stop automatically. This had no consequence as the cold box safety system acts to keep ...

  15. MAGNET

    CERN Multimedia

    B. Curé

    During the winter shutdown, the magnet subsystems went through a full maintenance. The magnet was successfully warmed up to room temperature beginning of December 2008. The vacuum was broken later on by injecting nitrogen at a pressure just above one atmosphere inside the vacuum tank. This was necessary both to prevent any accidental humidity ingress, and to allow for a modification of the vacuum gauges on the vacuum tank and maintenance of the diffusion pumps. The vacuum gauges had to be changed, because of erratic variations on the measurements, causing spurious alarms. The new type of vacuum gauges has been used in similar conditions on the other LHC experiments and without problems. They are shielded against the stray field. The lubricants of the primary and diffusion pumps have been changed. Several minor modifications were also carried out on the equipment in the service cavern, with the aim to ease the maintenance and to allow possible intervention during operation. Spare sensors have been bought. Th...

  16. Evaluation of endorectal magnetic resonance imaging and magnetic resonance spectroscopic imaging in diagnosing and staging prostate cancer - a prospective pilot study.

    Directory of Open Access Journals (Sweden)

    M Dholakia

    2005-01-01

    Full Text Available Aims: The main objective of our study was to evaluate the efficacy of End. MRI and MRSI in (1 detecting and (2 staging prostate cancer by correlating it with histopathological results. Methods: In a double blind prospective study of 20 patients were divided into two groups. In group A with 10 patients, the inclusion criteria were elevated PSA and/or a palpable nodule. All 10 patients with undiagnosed prostate cancer underwent End. MRI and MRSI followed by TRUS guided ten quadrant biopsy. In group B, 10 patients with already proven carcinoma prostate were included. All these patients underwent End. MRI and MRSI followed by radical prostatectomy. Results: The mean S.PSA was 19.8 ng/ml (1.9-52 and the mean Gleason score was 6.8 (5-8. In group A End. MRI/MRSI revealed a diagnosis of prostate cancer in 10 patients, but only six were positive on biopsy. In group B, End. MRI/MRSI showed eight patients to have periprostatic extension but only three were confirmed on final histology. Out of the eight patients that showed periprostatic spread on End. MRI/MRSI, seven patients showed seminal vesicle invasion, and one patient showed capsular infiltration. But on histopathology study seminal vesicle involvement was confirmed in only one patient and only two patients had capsular infiltration. Conclusions: This pilot study reveals that End.MRI/MRSI, although a relatively well-established investigation in the west, has not shown the same degree of accuracy in our setup.

  17. Staging of Hepatic Fibrosis: Comparison of Magnetic Resonance Elastography and Shear Wave Elastography in the Same Individuals

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Jeong Hee [Department of Radiology, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Lee, Jeong Min [Department of Radiology, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Woo, Hyun Sik; Yu, Mi Hye; Joo, Ijin; Lee, Eun Sun; Sohn, Ji Young [Department of Radiology, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Lee, Kyung Boon [Department of Pathology, Seoul National University Hospital, Seoul 110-744 (Korea, Republic of); Han, Joon Koo; Choi, Byung Ihn [Department of Radiology, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of); Institute of Radiation Medicine, Seoul National University College of Medicine, Seoul 110-744 (Korea, Republic of)

    2013-07-01

    To cross-validate liver stiffness (LS) measured on shear wave elastography (SWE) and on magnetic resonance elastography (MRE) in the same individuals. We included 94 liver transplantation (LT) recipients and 114 liver donors who underwent either MRE or SWE before surgery or biopsy. We determined the technical success rates and the incidence of unreliable LS measurements (LSM) of SWE and MRE. Among the 69 patients who underwent both MRE and SWE, the median and coefficient of variation (CV) of the LSM from each examination were compared and correlated. Areas under the receiver operating characteristic curve in both examinations were calculated in order to exclude the presence of hepatic fibrosis (HF). The technical success rates of MRE and SWE were 96.4% and 92.2%, respectively (p = 0.17), and all of the technical failures occurred in LT recipients. SWE showed 13.1% unreliable LSM, whereas MRE showed no such case (p < 0.05). There was moderate correlation in the LSM in both examinations (r = 0.67). SWE showed a significantly larger median LSM and CV than MRE. Both examinations showed similar diagnostic performance for excluding HF (Az; 0.989, 1.000, respectively). MRE and SWE show moderate correlation in their LSMs, although SWE shows higher incidence of unreliable LSMs in cirrhotic liver.

  18. Diagnostic accuracy of computed tomography and magnetic resonance imaging obtained after neoadjuvant chemoradiotherapy in predicting the local tumor stage and circumferential resection margin status of rectal cancer

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Hoon; Kim, Young Hoon; Lee, Yoon Jin; Lee, Kyoung Ho; Kang, Sung Bum; Kim, Duck Woo; Kim, Jae Hyun; Kim, Jae Sung; Lee, Hye Seung [Dept. of Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam (Korea, Republic of); Lee, Sang Min [Dept. of Radiology, Seoul National University Hospital, Seoul (Korea, Republic of)

    2014-02-15

    To measure the diagnostic accuracy of computed tomography (CT) and magnetic resonance imaging (MRI) obtained after neoadjuvant chemoradiotherapy (CRT) in patients with rectal cancer for a prediction of the local tumor stage and circumferential resection margin (CRM). Two independent radiologists reviewed CT and MRI obtained after neoadjuvant CRT. The accuracy of the local tumor staging and the diagnostic performance for the prediction of CRM involvement were calculated. The agreement between the measurements of the distance to potential CRM on both imaging modalities and the histopathology findings was assessed using Bland-Altman plots. 57 patients (mean age, 59.2 years; 24 females) were included. The accuracy of T and N staging were 43.9% (95% confidence interval, 30.8-57.7%) and 77.2% (64.2-87.3%) on CT and 63.2% (49.4-75.6%) and 77.2% (64.2-87.3%) on MRI for Observer 1. The accuracy of T and N staging were 54.4% (40.7-67.7%) and 77.2% (64.2-87.3%) on CT and 68.4% (54.7-80.1%) and 80.7% (68.1-90.0%) on MRI for Observer 2. Sensitivity and specificity on CRM involvement were 83.3% (43.7-97.0%) and 88.2% (76.6-94.5%) on CT and 100% (61.0-100%) and 90.2% (79.0-95.7%) on MRI for Observer 1. Sensitivity and specificity on CRM involvement were 66.7% (30.0-90.3%) and 88.2% (76.7-94.5%) on CT and 100% (61.0-100%) and 90.2% (79.0-95.7%) on MRI for Observer 2. Bland-Altman plots showed wide discrepancies between measurements of the distance to CRM on each CT and MRI and those on histopathology findings. CT and MRI showed limited performance in predicting the local tumor staging and CRM involvement in patients with neoadjuvant CRT although MRI tended to show a better performance than CT.

  19. Altered default mode network configuration in posttraumatic stress disorder after earthquake: A resting-stage functional magnetic resonance imaging study.

    Science.gov (United States)

    Zhang, Xiao-Dong; Yin, Yan; Hu, Xiao-Lei; Duan, Lian; Qi, Rongfeng; Xu, Qiang; Lu, Guang-Ming; Li, Ling-Jiang

    2017-09-01

    The neural substrates of posttraumatic stress disorder (PTSD) are still not fully elucidated. Hence, this study is to explore topological alterations of the default mode network (DMN) in victims with PTSD after a magnitude of 8.0 earthquake using resting-state functional magnetic resonance imaging (rs-fMRI).This study was approved by the local ethical review board, and all participants signed written informed consent. Sixty-two PTSD victims from the 2008 Sichuan earthquake and 62 matched exposed controls underwent rs-fMRI. PTSD was diagnosed by Clinician-Administered PTSD Scale, and underwent PTSD Checklist-Civilian Version for symptom scoring. The DMN was analyzed by using graph theoretical approaches. Further, Pearson correlation analysis was performed to correlate neuroimaging metrics to neuropsychological scores in victims with PTSD.Victims with PTSD showed decreased DMN functional connectivity strength between the right superior frontal gyrus and left inferior parietal lobule (IPL), and showed increased functional connectivity between the right IPL and precuneus or left posterior cingulate cortex. It was also found that victims with PTSD exhibited decreased nodal efficiency in right superior frontal gyrus and precuneus, and increased nodal efficiency in right hippocampus/parahippocampus. Apart from that, PTSD showed higher nodal degree in bilateral hippocampus/parahippocampus. In addition, the functional connectivity strength between the right IPL and precuneus correlated negatively to the avoid scores (r = -0.26, P = .04).This study implicates alteration of topological features on the DMN in PTSD victims after major earthquake, and provides new insights into DMN malfunction in PTSD based on graph theory.

  20. Comparison of Transcranial Magnetic Stimulation and Electroneuronography Between Bell's Palsy and Ramsay Hunt Syndrome in Their Acute Stages

    Science.gov (United States)

    Hur, Dong Min; Lee, Young Hee; Kim, Sung Hoon; Park, Jung Mi; Kim, Ji Hyun; Yong, Sang Yeol; Shinn, Jong Mock; Oh, Kyung Joon

    2013-01-01

    Objective To examine the neurophysiologic status in patients with idiopathic facial nerve palsy (Bell's palsy) and Ramsay Hunt syndrome (herpes zoster oticus) within 7 days from onset of symptoms, by comparing the amplitude of compound muscle action potentials (CMAP) of facial muscles in electroneuronography (ENoG) and transcranial magnetic stimulation (TMS). Methods The facial nerve conduction study using ENoG and TMS was performed in 42 patients with Bell's palsy and 14 patients with Ramsay Hunt syndrome within 7 days from onset of symptoms. Denervation ratio was calculated as CMAP amplitude evoked by ENoG or TMS on the affected side as percentage of the amplitudes on the healthy side. The severity of the facial palsy was graded according to House-Brackmann facial grading scale (H-B FGS). Results In all subjects, the denervation ratio in TMS (71.53±18.38%) was significantly greater than the denervation ratio in ENoG (41.95±21.59%). The difference of denervation ratio between ENoG and TMS was significantly smaller in patients with Ramsay Hunt syndrome than in patients with Bell's palsy. The denervation ratio of ENoG or TMS did not correlated significantly with the H-B FGS. Conclusion In the electrophysiologic study for evaluation in patients with facial palsy within 7 days from onset of symptoms, ENoG and TMS are useful in gaining additional information about the neurophysiologic status of the facial nerve and may help to evaluate prognosis and set management plan. PMID:23525840

  1. Molecular magnetic resonance imaging of activated hepatic stellate cells with ultrasmall superparamagnetic iron oxide targeting integrin αvβ3 for staging liver fibrosis in rat model

    Directory of Open Access Journals (Sweden)

    Zhang C

    2016-03-01

    Full Text Available Caiyuan Zhang,1,* Huanhuan Liu,1,* Yanfen Cui,1,* Xiaoming Li,1 Zhongyang Zhang,1 Yong Zhang,2 Dengbin Wang1 1Department of Radiology, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, 2MR Advanced Application and Research Center, GE Healthcare China, Shanghai, People’s Republic of China *These authors contributed equally to this work Purpose: To evaluate the expression level of integrin αvβ3 on activated hepatic stellate cells (HSCs at different stages of liver fibrosis induced by carbon tetrachloride (CCl4 in rat model and the feasibility to stage liver fibrosis by using molecular magnetic resonance imaging (MRI with arginine-glycine-aspartic acid (RGD peptide modified ultrasmall superparamagnetic iron oxide nanoparticle (USPIO specifically targeting integrin αvβ3.Materials and methods: All experiments received approval from our Institutional Animal Care and Use Committee. Thirty-six rats were randomly divided into three groups of 12 subjects each, and intraperitoneally injected with CCl4 for either 3, 6, or 9 weeks. Controls (n=10 received pure olive oil. The change in T2* relaxation rate (ΔR2* pre- and postintravenous administration of RGD-USPIO or naked USPIO was measured by 3.0T clinical MRI and compared by one-way analysis of variance or the Student’s t-test. The relationship between expression level of integrin αvβ3 and liver fibrotic degree was evaluated by Spearman’s ranked correlation.Results: Activated HSCs were confirmed to be the main cell types expressing integrin αvβ3 during liver fibrogenesis. The protein level of integrin αv and β3 subunit expressed on activated HSCs was upregulated and correlated well with the progression of liver fibrosis (r=0.954, P<0.001; r=0.931, P<0.001, respectively. After injection of RGD-USPIO, there is significant difference in ΔR2* among rats treated with 0, 3, 6, and 9 weeks of CCl4 (P<0.001. The accumulation of iron particles in fibrotic liver specimen is

  2. Positron Emission Tomography/Magnetic Resonance Imaging for Local Tumor Staging in Patients With Primary Breast Cancer: A Comparison With Positron Emission Tomography/Computed Tomography and Magnetic Resonance Imaging.

    Science.gov (United States)

    Grueneisen, Johannes; Nagarajah, James; Buchbender, Christian; Hoffmann, Oliver; Schaarschmidt, Benedikt Michael; Poeppel, Thorsten; Forsting, Michael; Quick, Harald H; Umutlu, Lale; Kinner, Sonja

    2015-08-01

    This study aimed to assess the diagnostic performance of integrated positron emission tomography (PET)/magnetic resonance imaging (MRI) of the breast for lesion detection and local tumor staging of patients with primary breast cancer in comparison to PET/computed tomography (CT) and MRI. The study was approved by the local institutional review board. Forty-nine patients with biopsy-proven invasive breast cancer were prospectively enrolled in our study. All patients underwent a PET/CT, and subsequently, a contrast-enhanced PET/MRI of the breast after written informed consent was obtained before each examination. Two radiologists independently evaluated the corresponding data sets (PET/CT, PET/MRI, and MRI) and were instructed to identify primary tumors lesions as well as multifocal/multicentric and bilateral disease. Furthermore, the occurrence of lymph node metastases was assessed, and the T-stage for each patient was determined. Histopathological verification of the local tumor extent and the axillary lymph node status was available for 30 of 49 and 48 of 49 patients, respectively. For the remaining patients, a consensus characterization was performed for the determination of the T-stage and nodal status, taking into account the results of clinical staging, PET/CT, and PET/MRI examinations. Statistical analysis was performed to test for differences in diagnostic performance between the different imaging procedures. P values less than 0.05 were considered to be statistically significant. Positron emission tomography/MRI and MRI correctly identified 47 (96%) of the 49 patients with primary breast cancer, whereas PET/CT enabled detection of 46 (94%) of 49 breast cancer patients and missed a synchronous carcinoma in the contralateral breast in 1 patient. In a lesion-by-lesion analysis, no significant differences could be obtained between the 3 imaging procedures for the identification of primary breast cancer lesions (P > 0.05). Positron emission tomography/MRI and

  3. MAGNET

    CERN Multimedia

    B. Curé

    The first phase of the commissioning ended in August by a triggered fast dump at 3T. All parameters were nominal, and the temperature recovery down to 4.5K was carried out in two days by the cryogenics. In September, series of ramps were achieved up to 3 and finally 3.8T, while checking thoroughly the detectors in the forward region, measuring any movement of and around the HF. After the incident of the LHC accelerator on September 19th, corrective actions could be undertaken in the forward region. When all these displacements were fully characterized and repetitive, with no sign of increments in displacement at each field ramp, it was possible to start the CRAFT, Cosmic Run at Four Tesla (which was in fact at 3.8T). The magnet was ramped up to 18.16kA and the 3 week run went smoothly, with only 4 interruptions: due to the VIP visits on 21st October during the LHC inauguration day; a water leak on the cooling demineralized water circuit, about 1 l/min, that triggered a stop of the cooling pumps, and resulte...

  4. MAGNET

    CERN Multimedia

    Benoit Curé

    The cooling down to the nominal temperature of 4.5 K was achieved at the beginning of August, in conjunction with the completion of the installation work of the connection between the power lines and the coil current leads. The temperature gradient on the first exchanger of the cold box is now kept within the nominal range. A leak of lubricant on a gasket of the helium compressor station installed at the surface was observed and several corrective actions were necessary to bring the situation back to normal. The compressor had to be refilled with lubricant and a regeneration of the filters and adsorbers was necessary. The coil cool down was resumed successfully, and the cryogenics is running since then with all parameters being nominal. Preliminary tests of the 20kA coil power supply were done earlier at full current through the discharge lines into the dump resistors, and with the powering busbars from USC5 to UXC5 without the magnet connected. On Monday evening August 25th, at 8pm, the final commissionin...

  5. MAGNET

    CERN Multimedia

    Benoit Curé

    2013-01-01

    Maintenance work and consolidation activities on the magnet cryogenics and its power distribution are progressing according to the schedules. The manufacturing of the two new helium compressor frame units has started. The frame units support the valves, all the sensors and the compressors with their motors. This activity is subcontracted. The final installation and the commissioning at CERN are scheduled for March–April 2014. The overhauls of existing cryogenics equipment (compressors, motors) are in progress. The reassembly of the components shall start in early 2014. The helium drier, to be installed on the high-pressure helium piping, has been ordered and will be delivered in the first trimester of 2014. The power distribution for the helium compressors in SH5 on the 3.3kV network is progressing. The 3.3kV switches, between each compressor and its hot spare compressor, are being installed, together with the power cables for the new compressors. The 3.3kV electrical switchboards in SE5 will ...

  6. [Post-stroke dysphagia in chronic stage treated with magnetic-ball sticking therapy at the auricular points: a randomized controlled trial].

    Science.gov (United States)

    Jin, Hai-Peng; Wu, Qiu-Yan; Zhang, Wei; Xie, Jun-Jie; Chen, Jin-Chun

    2014-01-01

    To assess the effectiveness and safety on post-stroke dysphagia in chronic stage treated with magnetic-ball sticking therapy at the auricular points. Ninety cases of post-apoplexy dysphagia in chronic stage were randomized into an auricular points group and an acupuncture group. In the auricular points group, the magnetic-ball sticking therapy was applied to subcortex (pizhixia, AT4), brainstem (naogan, AT(3,4i)), mouth (kou, CO1), cheek (mianjia, LO(5,6i)), tongue (she, LO2) and throat (yanhou, TG3) on one ear each time, and were changed on the other ear once every 3 days. In the acupucnture group, acupuncture was applied to Feng-chi (GB 20), Yifeng (TE 17), Shanglianquan (Extra), Jinjin (EX-HN 12), Yuye (EX-HN 13), Shuigou (GV 26) and Tongli (TH 5), etc. The needles were retained for 30 min in each treatment. The treatment was gi-yen once a day in the two groups and the treatment of 6 days made one session. There was 1 day at an interval among the sessions. Totally, 3 sessions of treatment were required. The video fluoroscopic swallowing study (VFSS) was performed for 4 kinds of food with different properties and shapes in each patient. The main indices were Rosenbek penetration-aspiration score, oral-retaining score and throat-retaining score. The efficacy, and the incidences of aspiration pneumonia and malnutrition were compared between the two groups. The nutrition indices were compared before and after treatment between the two groups, such as the skinfold thickness of triceps brachii muscle, serum albumin and peralbumin. In 21 days of treatment, in the auricular points group, the 1 mL liquid loversol Rosenbek penetration-aspiration score (1.51 +/- 0.69), oral-retaining score (1.17 +/- 0.38) and throat-retaining score (1.30 +/- 0.66) were all lower than those (2.51 +/- 0.67, 1.63 +/- 0.72, 1.67 +/- 0.7) in the acupuncture group separately. The 10 mL liquid loversol Rosenbek penetration-aspiration score (2.27 +/- 0.65), oral-retaining score (1.60 +/- 0.50) and

  7. Comparative study of the detection of joint injury in early-stage rheumatoid arthritis by magnetic resonance imaging of the wrist and finger joints and physical examination.

    Science.gov (United States)

    Tamai, Mami; Kawakami, Atsushi; Iwamoto, Naoki; Kawashiri, Shin-Ya; Fujikawa, Keita; Aramaki, Toshiyuki; Kita, Junko; Okada, Akitomo; Koga, Tomohiro; Arima, Kazuhiko; Kamachi, Makoto; Yamasaki, Satoshi; Nakamura, Hideki; Ida, Hiroaki; Origuchi, Tomoki; Takao, Shoichiro; Aoyagi, Kiyoshi; Uetani, Masataka; Eguchi, Katsumi

    2011-03-01

    To verify whether magnetic resonance imaging (MRI)-proven joint injury is sensitive as compared with joint injury determined by physical examination. MRI of the wrist and finger joints of both hands was examined in 51 early-stage rheumatoid arthritis (RA) patients by both plain and gadolinium diethylenetriaminepentaacetic acid-enhanced MRI. Synovitis, bone edema, and bone erosion (the latter two included as bone lesions at the wrist joints); metacarpophalangeal joints; and proximal interphalangeal joints were considered as MRI-proven joint injury. Japan College of Rheumatology-certified rheumatologists had given a physical examination just before the MRI study. The presence of tender and/or swollen joints in the same fields as MRI was considered as joint injury on physical examination. The association of MRI-proven joint injury with physical examination-proven joint injury was examined. A total of 1,110 sites were available to be examined. MRI-proven joint injury was found in 521 sites, whereas the other 589 sites were normal. Physical examination-proven joint injury was found in 305 sites, which was significantly low as compared with MRI-proven joint injury (P = 1.1 × 10(-12) versus MRI). Joint injury on physical examination was not found in 81.5% of the sites where MRI findings were normal. Furthermore, an association of the severity of MRI-proven joint injury with that of joint injury on physical examination was clearly demonstrated (P = 1.6 × 10(-15), r(s) = 0.469). Our present data suggest that MRI is not only sensitive but accurately reflects the joint injury in patients with early-stage RA. Copyright © 2011 by the American College of Rheumatology.

  8. Evaluate the early changes of myocardial fibers in rhesus monkey during sub-acute stage of myocardial infarction using diffusion tensor magnetic resonance imaging.

    Science.gov (United States)

    Wang, Yuqing; Cai, Wei; Wang, Lei; Xia, Rui

    2016-05-01

    The deterioration of cardiac mechanical function starts from the micro-alterations in the myocardial fibers after myocardial infarction (MI) due to the heart beats derived from the systole and diastole of the myocardial fibers. So, we want to evaluate quantitatively the early changes of myocardial fibers in rhesus monkey during sub-acute MI stage. Three fixed hearts with infarction after left anterior descending coronary artery ligation for 7days and eight age-matched intact controls were scanned by ex-vivo diffusion tensor magnetic resonance imaging (DT-MRI) to measure apparent diffusion coefficient (ADC), fractional anisotropy (FA) and helix angle (HA). In comparison with healthy controls, FA and transmural range of HA in MI regions showed a significant reduction whereas ADC showed a significant increment (pmyocardial fibers shifted further to left-handed helix around the infarcted and adjacent myocardium but shifted further to right-handed helix in remote myocardium. HA is sensitive to evaluate quantitatively the early changes of myocardial fibers in sub-acute MI rhesus monkeys. The myocardial fibers in normal monkeys are similar to those in normal humans, suggesting that early changes of myocardial fibers in sub-acute MI monkeys can contribute to more accurately understand those in patients suffering sub-acute MI. Copyright © 2015 Elsevier Inc. All rights reserved.

  9. Equipartition and transport in two-dimensional electrostatic turbulence

    DEFF Research Database (Denmark)

    Naulin, V.; Nycander, J.; Juul Rasmussen, J.

    1998-01-01

    Turbulent equipartition is investigated for the nonlinear evolution of pressure driven flute modes of a plasma in an inhomogeneous magnetic field. The Rayleigh-Taylor instability is recovered by linear stability analysis, and occurs when the pressure profile is more peaked than the profile of the...

  10. Integrated code development for studying laser driven plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Takabe, Hideaki; Nagatomo, Hideo; Sunahara, Atsusi; Ohnishi, Naofumi; Naruo, Syuji; Mima, Kunioki [Osaka Univ., Suita (Japan). Inst. of Laser Engineering

    1998-03-01

    Present status and plan for developing an integrated implosion code are briefly explained by focusing on motivation, numerical scheme and issues to be developed more. Highly nonlinear stage of Rayleigh-Taylor instability of ablation front by laser irradiation has been simulated so as to be compared with model experiments. Improvement in transport and rezoning/remapping algorithms in ILESTA code is described. (author)

  11. Prospective Validation of a Low Rectal Cancer Magnetic Resonance Imaging Staging System and Development of a Local Recurrence Risk Stratification Model: The MERCURY II Study.

    Science.gov (United States)

    Battersby, Nicholas J; How, Peter; Moran, Brendan; Stelzner, Sigmar; West, Nicholas P; Branagan, Graham; Strassburg, Joachim; Quirke, Philip; Tekkis, Paris; Pedersen, Bodil Ginnerup; Gudgeon, Mark; Heald, Bill; Brown, Gina

    2016-04-01

    This study aimed to validate a magnetic resonance imaging (MRI) staging classification that preoperatively assessed the relationship between tumor and the low rectal cancer surgical resection plane (mrLRP). Low rectal cancer oncological outcomes remain a global challenge, evidenced by high pathological circumferential resection margin (pCRM) rates and unacceptable variations in permanent colostomies. Between 2008 and 2012, a prospective, observational, multicenter study (MERCURY II) recruited 279 patients with adenocarcinoma 6 cm or less from the anal verge. MRI assessed the following: mrLRP "safe or unsafe," venous invasion (mrEMVI), depth of spread, node status, tumor height, and tumor quadrant. MRI-based treatment recommendations were compared against final management and pCRM outcomes. Overall pCRM involvement was 9.0% [95% confidence interval (CI), 5.9-12.3], significantly lower than previously reported rates of 30%. Patients with no adverse MRI features and a "safe" mrLRP underwent sphincter-preserving surgery without preoperative radiotherapy, resulting in a 1.6% pCRM rate. The pCRM rate increased 5-fold for an "unsafe" compared with "safe" preoperative mrLRP [odds ratio (OR) = 5.5; 95% CI, 2.3-13.3)]. Posttreatment MRI reassessment indicated a "safe" ymrLRP in 33 of 113 (29.2%), none of whom had ypCRM involvement. In contrast, persistent "unsafe" ymrLRP posttherapy resulted in 17.5% ypCRM involvement. Further independent MRI assessed risk factors were EMVI (OR = 3.8; 95% CI, 1.5-9.6), tumors less than 4.0 cm from the anal verge (OR = 3.4; 95% CI, 1.3-8.8), and anterior tumors (OR = 2.8; 95% CI, 1.1-6.8). The study validated MRI low rectal plane assessment, reducing pCRM involvement and avoiding overtreatment through selective preoperative therapy and rationalized use of permanent colostomy. It also highlights the importance of posttreatment restaging.

  12. Multiple stage railgun

    International Nuclear Information System (INIS)

    Aaland, K.; Hawke, R.S.; Scudder, J.K.

    1982-01-01

    A multiple stage magnetic railgun accelerator for accelerating a projectile by movement of a plasma arc along the rails. The railgun is divided into a plurality of successive rail stages which are sequentially energized by separate energy sources as the projectile moves through the bore of the railgun. Propagation of energy from an energized rail stage back towards the breech end of the railgun can be prevented by connection of the energy sources to the rails through isolation diodes. Propagation of energy from an energized rail stage back towards the breech end of the railgun can also be prevented by dividing the rails into electrically isolated rail sections. In such case means are used to extinguish the arc at the end of each energized stage and a fuse or laser device is used to initiate a new plasma arc in the next energized rail stage

  13. Stage theta pinch experiments

    International Nuclear Information System (INIS)

    Linford, R.K.; Downing, J.N.; Gribble, R.F.; Jacobson, A.R.; Platts, D.A.; Thomas, K.S.

    1975-01-01

    The Staged Theta Pinch program is designed to study the technological and physics problems associated with producing fat plasmas and separating the implosion heating from the adiabatic compression. Several methods of implosion heating are discussed. Circuit diagrams and theoretical magnetic field behavior are described for the STP and resonant heating experiments. (MOW)

  14. The build oxygenation T{sub 2}{sup *} values of resectable esophageal squamous cell carcinomas as measured by 3T magnetic resonance imaging: Association with tumor stage

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Yu Lian; Zhang, Xiao Ming; Huang, Yu Cheng; Chen, Tian Wu; Chen, Yan Il; Chen, Fan; Zeng, Nan Lin; Li, Rui [Sichuan Key Laboratory of Medical Imaging, Affiliated Hospital of North Sichuan Medical College, Nanchong (China); Yang, Zhi Gang [Dept. of Radiology, West China Hospital of Sichuan University, Chengdu (China); Hu, Jiani [Dept. of Radiology, Wayne State University, Detroit (United States)

    2017-08-01

    To explore the association between the blood oxygenation T{sub 2}{sup *} values of resectable esophageal squamous cell carcinomas (ESCCs) and tumor stages. This study included 48 ESCC patients and 20 healthy participants who had undergone esophageal T{sub 2}{sup *} -weighted imaging to obtain T{sub 2}{sup *} values of the tumors and normal esophagus. ESCC patients underwent surgical resections less than one week after imaging. Statistical analyses were performed to identify the association between T{sub 2}{sup *} values of ESCCs and tumor stages. One-way ANOVA and Student-Newman-Keuls tests revealed that the T{sub 2}{sup *} value could differentiate stage T1 ESCCs (17.7 ± 3.3 ms) from stage T2 and T3 tumors (24.6 ± 2.7 ms and 27.8 ± 5.6 ms, respectively; all ps < 0.001). Receiver operating curve (ROC) analysis showed the suitable cutoff T{sub 2}{sup *} value of 21.3 ms for either differentiation. The former statistical tests demonstrated that the T{sub 2}{sup *} value could not differentiate between stages T2 and T3 (24.6 ± 2.7 ms vs. 27.8 ± 5.6 ms, respectively, p > 0.05) or between N stages (N1 vs. N2 vs. N3: 24.7 ± 6.9 ms vs. 25.4 ± 4.5 ms vs. 26.8 ± 3.9 ms, respectively; all ps > 0.05). The former tests illustrated that the T{sub 2}{sup *} value could differentiate anatomic stages I and II (18.8 ± 4.8 ms and 26.9 ± 5.9 ms, respectively) or stages I and III (27.3 ± 3.6 ms). ROC analysis depicted the same cutoff T{sub 2}{sup *} value of 21.3 ms for either differentiation. In addition, the Student's t test revealed that the T{sub 2}{sup *} value could determine grouped T stages (T0 vs. T1–3: 17.0 ± 2.9 ms vs. 25.2 ± 6.2 ms; T0–1 vs. T2–3: 17.3 ± 3.0 ms vs. 27.1 ± 5.3 ms; and T0–2 vs. T3: 18.8 ± 4.2 ms vs. 27.8 ± 5.6 ms, all ps < 0.001). ROC analysis indicated that the T{sub 2}{sup *} value could detect ESCCs (cutoff, 20 ms), and discriminate between stages T0–1 and T2–3 (cutoff, 21.3 ms) and between T0–2 and T3 (cutoff, 20.4 ms

  15. Stage design

    International Nuclear Information System (INIS)

    Shacter, J.

    1975-01-01

    A method is described of cycling gases through a plurality of diffusion stages comprising the steps of admitting the diffused gases from a first diffusion stage into an axial compressor, simultaneously admitting the undiffused gases from a second diffusion stage into an intermediate pressure zone of said compressor corresponding in pressure to the pressure of said undiffused gases, and then admitting the resulting compressed mixture of diffused and undiffused gases into a third diffusion stage

  16. Are stage IV vestibular schwannomas preoperatively different from other stages?

    Science.gov (United States)

    Tringali, Stéphane; Dubreuil, Christian; Zaouche, Sandra; Ferber-Viart, Chantal

    2008-01-01

    The aim of this study was to focus on the clinical and paraclinical symptoms of patients suffering from Stage IV vestibular schwannomas (VSs). In this prospective study, we included 734 patients who have VS and candidates for operation. Patients were classified as having Stage I, II, III, or IV tumors according to Tos criteria as evaluated by magnetic resonance imaging. PREOPERATIVE CLINICAL EVALUATION: We recorded the occurrence of complaints (%) and duration (yr) of hearing loss, tinnitus, and balance disorder. Preoperative paraclinical evaluation included pure-tone (PTA) and speech audiometry, auditory brainstem response (ABR) patterns, and vestibular deficit at videonystamography (VNG). Continuous variables were compared between Stage IV and other stages using analysis of variance. Qualitative variables expressed as a percentage of presence were compared between Stage IV and other stages using percentage comparison. Quantitative Parameters. Patients with Stage IV VS were significantly younger as compared with patients with other stages. Stage IV hearing loss was greater compared with other stages at 250 and 500 Hz but smaller at 2,000 and 8,000 Hz. We found no difference in the loss of PTA between Stage IV and the other stages. Speech discriminancy score was smaller in Stage IV. The durations of hearing loss, tinnitus, and balance disorders were similar whatever the tumor stage. Auditory brainstem response patterns showed no difference in Wave III latency between Stage IV VS and other stages, whereas Wave V latency and V-I interval were higher in Stage IV. Both ABR threshold and VNG caloric deficit were higher in Stage IV VS compared with other stages. Qualitative Parameters. The percentage of patients with Stage IV was lower than that with Stages II and III. The percentage of men and women was similar in all stages. The occurrence of hearing loss was similar in all stages, whereas that of tinnitus was lower in Stage IV compared with Stages I and II. In

  17. Magnetic fields

    International Nuclear Information System (INIS)

    Mestel, L.; Arizona Univ., Tucson)

    1985-01-01

    The role of the Galactic magnetic field in the early stages of star formation is examined. The dynamical and observational consequences of the anisotropic collapse of cool gas clouds permeated by the local Galactic magnetic field are discussed. Magneto-gravitational equilibria of such clouds with subcritical mass-flux ratios, especially in the thin disk approximation, are addressed. Magnetic braking of both subcritical and supercritical masses is considered, and the consequences of flux leakage during the molecular cloud phase are discussed, including the effect on field topology

  18. Quantitative Ultrasound for Staging of Hepatic Steatosis in Patients on Home Parenteral Nutrition Validated with Magnetic Resonance Spectroscopy: A Feasibility Study

    NARCIS (Netherlands)

    Weijers, G.; Wanten, G.J.A.; Thijssen, J.M.; Graaf, M. van der; Korte, C.L. de

    2016-01-01

    Patients on home parenteral nutrition are at risk for developing liver dysfunction, which is due partly to the accumulation of lipids in the liver (steatosis) and may progress to end-stage liver disease with overt liver failure. Therefore, a timely diagnosis with easy access to repeated assessment

  19. Magnetic resonance imaging of the bone marrow following treatment with recombinant human erythropoietin in patients with end-stage renal disease

    DEFF Research Database (Denmark)

    Jensen, K E; Stenver, D; Jensen, M

    1990-01-01

    in the hemoglobin concentration in peripheral blood. The increase in T1 relaxation times, together with earlier reported changes observed with localized magnetic resonance spectroscopy, indicate an alteration in cellular composition of the hemopoietic bone marrow with an increase in the amount of hemopoietic active...... tissue. MRI may be a useful, non-invasive way of evaluating bone marrow response to different modes of rHuEPO administration and dosage....

  20. Coregistered whole body magnetic resonance imaging-positron emission tomography (MRI-PET) versus PET-computed tomography plus brain MRI in staging resectable lung cancer: comparisons of clinical effectiveness in a randomized trial.

    Science.gov (United States)

    Yi, Chin A; Lee, Kyung Soo; Lee, Ho Yun; Kim, Seonwoo; Kwon, O Jung; Kim, Hojoong; Choi, Joon Young; Kim, Byung-Tae; Hwang, Hye Sun; Shim, Young Mog

    2013-05-15

    The objective of this study was to assess whether coregistered whole brain (WB) magnetic resonance imaging-positron emission tomography (MRI-PET) would increase the number of correctly upstaged patients compared with WB PET-computed tomography (PET-CT) plus dedicated brain MRI in patients with nonsmall cell lung cancer (NSCLC). From January 2010 through November 2011, patients with NSCLC who had resectable disease based on conventional staging were assigned randomly either to coregistered MRI-PET or WB PET-CT plus brain MRI (ClinicalTrials.gov trial NCT01065415). The primary endpoint was correct upstaging (the identification of lesions with higher tumor, lymph node, or metastasis classification, verified with biopsy or other diagnostic test) to have the advantage of avoiding unnecessary thoracotomy, to determine appropriate treatment, and to accurately predict patient prognosis. The secondary endpoints were over staging and under staging compared with pathologic staging. Lung cancer was correctly upstaged in 37 of 143 patients (25.9%) in the MRI-PET group and in 26 of 120 patients (21.7%) in the PET-CT plus brain MRI group (4.2% difference; 95% confidence interval, -6.1% to 14.5%; P = .426). Lung cancer was over staged in 26 of 143 patients (18.2%) in the MRI-PET group and in 7 of 120 patients (5.8%) in the PET-CT plus brain MRI group (12.4% difference; 95% confidence interval, 4.8%-20%; P = .003), whereas lung cancer was under staged in 18 of 143 patients (12.6%) and in 28 of 120 patients (23.3%), respectively (-10.7% difference; 95% confidence interval, -20.1% to -1.4%; P = .022). Although both staging tools allowed greater than 20% correct upstaging compared with conventional staging methods, coregistered MRI-PET did not appear to help identify significantly more correctly upstaged patients than PET-CT plus brain MRI in patients with NSCLC. Copyright © 2013 American Cancer Society.

  1. Trading stages

    DEFF Research Database (Denmark)

    Steiner, Uli; Tuljapurkar, Shripad; Coulson, Tim

    2012-01-01

    because they are hard to use and interpret, and tools for age and stage structured populations are missing. We present easily interpretable expressions for the sensitivities and elasticities of life expectancy to vital rates in age-stage models, and illustrate their application with two biological......Interest in stage-and age structured models has recently increased because they can describe quantitative traits such as size that are left out of age-only demography. Available methods for the analysis of effects of vital rates on lifespan in stage-structured models have not been widely applied...... examples. Much of our approach relies on trading of time and mortality risk in one stage for time and risk in others. Our approach contributes to the new framework of the study of age- and stage-structured biodemography....

  2. The role of magnetic resonance imaging (MRI) and MRI-guided surgery in the evaluation of patients with early stage breast cancer for breast conserving therapy

    International Nuclear Information System (INIS)

    Tan, Jacqueline E.; Orel, Susan G.; Schnall, Mitchell D.; Solin, Lawrence J.

    1997-01-01

    Purpose: Mammography is the primary imaging modality for the detection of breast cancer and the evaluation of patients with early stage breast cancer for breast conserving therapy (BCT). MRI may be more sensitive than mammography for detecting breast cancer and may have an adjunctive role in assessing patients with early stage disease for BCT. Our experience with 83 patients undergoing breast MRI during consideration for breast conserving therapy is analyzed. Materials and Methods: We reviewed 83 consecutive cases of patients undergoing breast MRI during standard work-up and evaluation for BCT from 1993 to 1996. Analysis of cases was limited to women who were AJCC clinical Stage 0, I, or II and who received definitive therapy at our institution. All patients signed informed consent. MRI of the breast was performed at 1.5 Tesla. Sagittal T1 and T2 and 3-D gradient pre- and post-contrast images were obtained. All MRI studies were reviewed by two radiologists. All patients were evaluated by one radiation oncologist. The records of these 83 patients were reviewed for patient age, tumor size, AJCC stage, histology, physical examination findings, mammographic findings, ultrasound findings, MRI findings, timing of first MRI study with respect to excisional surgery, findings from MRI-guided surgery (when done), and whether the patient underwent BCT. Results: The median age at the time of presentation was 51.5 years (range 26-77 years). Of the 83 patients, 16% were AJCC clinical stage 0, 65% were stage I, and 19% were stage II. No patient presented with synchronous bilateral carcinoma. Two patients had a history of prior contralateral breast carcinoma; both received BCT for their initial disease. Sixteen percent of patients had intraductal carcinoma, 39% had intraductal and infiltrating carcinoma, 28% had infiltrating ductal carcinoma, 7% had infiltrating lobular carcinoma, 4% had tubular carcinoma, 2% had adenoid cystic carcinoma, 2% had medullary carcinoma, 1% had colloid

  3. Staging for vaginal cancer.

    Science.gov (United States)

    Rajaram, Shalini; Maheshwari, Amita; Srivastava, Astha

    2015-08-01

    Vaginal cancer is a rare cancer comprising about 3% of all gynecologic cancers. Primary vaginal cancer should be carefully assigned as spread from cervix, vulva, and other metastatic tumors to vagina can occur. Although vaginal cancer traditionally occurs in older postmenopausal women, the incidence of high-risk human papillomavirus (HPV)-induced cancers is increasing in younger women. Squamous cell carcinoma is still the most common histopathologic type followed by adenocarcinoma. With decreasing use of diethylstilbestrol in pregnancy, non-diethylstilbestrol-associated cancers are described. The Federation Internationale de Gynecologie et d'Obstetrique (FIGO) staging of vaginal cancer (2009) follows the same rules as cervical cancer; it is clinically staged and allows the use of routine investigative modalities for staging. Although FIGO encourages the use of advanced imaging modalities, such as computed tomography, magnetic resonance imaging (MRI), and positron emission tomography (PET), to guide therapy, the imaging findings may not be used to change or reassign the stage. TNM staging is the pathologic staging system proposed by the American Joint Committee on Cancer, and information available from examination of the resected specimen, including pelvic and inguinal lymph nodes, may be used for staging. Copyright © 2015 Elsevier Ltd. All rights reserved.

  4. Comparison of PET-CT and magnetic resonance diffusion weighted imaging with body suppression (DWIBS) for initial staging of malignant lymphomas

    Energy Technology Data Exchange (ETDEWEB)

    Stéphane, Velasco, E-mail: stephane.velasco@chu-poitiers.fr [Department of Radiology, CHU de Poitiers, rue de la milétrie, 86000 Poitiers (France); Samuel, Burg, E-mail: s.burg@chu-poitiers.fr [Department of Nuclear Medicine, CHU de Poitiers, rue de la milétrie, 86000 Poitiers (France); Department of Nuclear Medicine, Saint-Louis Hospital, Paris CHU Saint Louis, 40 rue de Bichat, 75 010 Paris (France); Vincent, Delwail, E-mail: v.delwail@chu-poitiers.fr [Department of Hematology, CHU de Poitiers, rue de la milétrie, 86000 Poitiers (France); Joelle, Guilhot, E-mail: j.guilhot@chu-poitiers.fr [Department of Hematology, CHU de Poitiers, rue de la milétrie, 86000 Poitiers (France); Remy, Perdrisot, E-mail: r.perdrisot@chu-poitiers.fr [Department of Nuclear Medicine, CHU de Poitiers, rue de la milétrie, 86000 Poitiers (France); Francois, Guilhot Gaudeffroy, E-mail: f.guilhot-gaudeffroy@chu-poitiers.fr [Department of Hematology, CHU de Poitiers, rue de la milétrie, 86000 Poitiers (France); Jean-Pierre, Tasu, E-mail: j.p.tasu@chu-poitiers.fr [Department of Radiology, CHU de Poitiers, rue de la milétrie, 86000 Poitiers (France)

    2013-11-01

    Objective: To evaluate the clinical impact of diffusion-weighted whole-body imaging with background body signal suppression (DWIBS) in staging of malignant lymphoma. Methods: Twenty-three patients with proven malignant lymphomas were prospectively enrolled. DWIBS (b = 0, 1000 s/mm{sup 2}) examinations and PET-CT were performed respectively on an Intera 1.5 T unit and a Gyroscan PET-CT scan (Philips Medical system, Best, the Netherland). The criteria for positive node involvement were a size over 10 mm or an apparent diffusion coefficient (ADC) value under 0.75 10{sup −3} mm{sup 2}/s for nodes under 10 mm. For extranodal analysis, a high or heterogeneous signal on DWIBS was considered as positive. In cases of discordance, the reference standard for each region or organ was established at 6 months after the diagnosis according to all available clinical, biological information, as well as histological evidence or follow-up to prove or disprove the presence of disease. Results: DWIBS and PET-CT results were congruent in 333 node regions on the 345 areas analyzed, with excellent agreement (κ = 0.97, P < 0.0001). From 433 organs analyzed (one patient had splenectomy) extranodal disease was detected in 22 organs on DWIBS. The two imaging techniques agreed on 430 organs (κ = 0.99, P < 0.0001). Finally, Ann Arbor stages based on DWIBS and those of PET/CT were in agreement for 23 patients. Conclusions: For malignant lymphoma in a pre-therapeutic context, agreement between diffusion-weighted whole-body imaging and PET/CT is high for Ann Arbor staging.

  5. High-End Concept Based on Hypersonic Two-Stage Rocket and Electro-Magnetic Railgun to Launch Micro-Satellites Into Low-Earth

    Science.gov (United States)

    Bozic, O.; Longo, J. M.; Giese, P.; Behren, J.

    2005-02-01

    The electromagnetic railgun technology appears to be an interesting alternative to launch small payloads into Low Earth Orbit (LEO), as this may introduce lower launch costs. A high-end solution, based upon present state of the art technology, has been investigated to derive the technical boundary conditions for the application of such a new system. This paper presents the main concept and the design aspects of such propelled projectile with special emphasis on flight mechanics, aero-/thermodynamics, materials and propulsion characteristics. Launch angles and trajectory optimisation analyses are carried out by means of 3 degree of freedom simulations (3DOF). The aerodynamic form of the projectile is optimised to provoke minimum drag and low heat loads. The surface temperature distribution for critical zones is calculated with DLR developed Navier-Stokes codes TAU, HOTSOSE, whereas the engineering tool HF3T is used for time dependent calculations of heat loads and temperatures on project surface and inner structures. Furthermore, competing propulsions systems are considered for the rocket engines of both stages. The structural mass is analysed mostly on the basis of carbon fibre reinforced materials as well as classical aerospace metallic materials. Finally, this paper gives a critical overview of the technical feasibility and cost of small rockets for such missions. Key words: micro-satellite, two-stage-rocket, railgun, rocket-engines, aero/thermodynamic, mass optimization

  6. Takotsubo cardiomyopathy, a two-stage recovery of left ventricular systolic and diastolic function as determined by cardiac magnetic resonance imaging

    DEFF Research Database (Denmark)

    Ahtarovski, Kiril Aleksov; Iversen, Kasper Karmark; Christensen, Thomas Emil

    2014-01-01

    AIMS: Takotsubo cardiomyopathy (TTC) is an entity mimicking acute myocardial infarction, characterized by transient severe systolic heart failure. Echocardiographic studies suggest that diastolic dysfunction is present in TTC at presentation; however, no reports exist regarding the time course...... of left ventricular (LV) recovery. This study describes the recovery of LV systolic and diastolic function in TTC. We hypothesized that, in TTC, there is diastolic dysfunction at admission, and that recovery is delayed compared with systolic function. METHODS AND RESULTS: We enrolled (consecutively 2010......-12) 16 patients (mean age 66, range 39-84 years) diagnosed with TTC and 20 healthy matched controls. We performed cardiac magnetic resonance imaging (CMR) at admission, pre-discharge, and 3-month follow-up. Diastolic function was assessed by LV peak filling rate (LVPFR) and left atrial (LA) emptying...

  7. Specific proof of various stages of Osler's disease of the brain via high field magnetic resonance tomography (1. 5 Tesla)

    Energy Technology Data Exchange (ETDEWEB)

    Billet, F.; Bluemm, R.G.; Beyer, H.K.

    1988-08-01

    MR is a sensitive noninvasive examination method for diagnosing parenchymatous cryptic arteriovenous malformations and sequels of cerebral haemorrhage. In a patient with recurring nosebleed and brain stem syndrome eleven so-called cryptic arteriovenous malformations or their haemorrhage sequels were diagnosed via magnetic resonance tomography. Basing on these specific findings, nosebleeding, and a positive family anamnesis, the findings could be classified as belonging to manifestations of Osler's disease (hereditary haemorrhagic telangiectasia). This rare disease is characterised by a triad of signs: telangiectasias, recurring bleeding, and heredity. In this article the specific MR image is compared with the CT pattern and the results are discussed against the background of literature on Osler's disease which is also known as Rendu-Osler-Weber disease.

  8. Staging atmospheres

    DEFF Research Database (Denmark)

    Bille, Mikkel; Bjerregaard, Peter; Sørensen, Tim Flohr

    2015-01-01

    The article introduces the special issue on staging atmospheres by surveying the philosophical, political and anthropological literature on atmosphere, and explores the relationship between atmosphere, material culture, subjectivity and affect. Atmosphere seems to occupy one of the classic...

  9. Endometrial carcinoma: merit of magnetic resonance in pre-surgical staging; Carcinoma de endometrio: valor de la estadificacion prequirurgica por resonancia magnetica

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez, E.; Barrera, M. C.; Gervas, C.; Salvador, E.; Rivero, B. [Hospital Donostia. San sebastian (Spain); Sentis, M. [Corporacio Sanitaria Pare Tauli. Sabadell (Spain)

    2003-07-01

    To evaluate MR capacity in assessing deep myometrial and cervical infiltrations in cases of endometrial carcinoma. A series of 30 consecutively diagnosed endometrial cancer patients was pre-surgically evaluated by means of magnetic resonance (MR). TSE-T2 sequences with fat saturation and dynamic FFe sequence were used after gadolinium administration. A correlation with post-surgical histological stating was made. There were then determined sensitivity (S), specificity (SP), positive predictive value (PPV) and negative predictive value (NPV) for the deep myometrial infiltration and cervical invasion. Cases of overestimation and underestimation were analyzed. Values obtained for myometrium and cervix were, respectively, S of 67% and 63%, SP of 89% and 91%, PPV of 80% and 71% and NPV of 80% and 87%. Two cases each were over valued for myometrial infiltration and cervix: four cases and 3 cases, respectively, were undervalues. MR stating in cases of endometrial carcinoma is a highly reliable diagnostic technique, but it does present certain limitations. (Author) 19 refs.

  10. Impact of the integration of proton magnetic resonance imaging spectroscopy to PI-RADS 2 for prediction of high grade and high stage prostate cancer

    Energy Technology Data Exchange (ETDEWEB)

    Leapman, Michael S.; Wang, Zhen J.; Behr, Spencer C.; Kurhanewicz, John; Zagoria, Ronald J.; Carroll, Peter R.; Westphalen, Antonio C., E-mail: antonio.westphalen@ucsf.edu [University of California, San Francisco, CA (United States)

    2017-09-15

    Objective: To compare the predictions of dominant Gleason pattern ≥ 4 or non-organ confined disease with Prostate Imaging Reporting and Data System (PI-RADS v2) with or without proton magnetic resonance spectroscopic imaging ({sup 1}H-MRSI). Materials and Methods: Thirty-nine men underwent 3-tesla endorectal multiparametric MRI including {sup 1}H-MRSI and prostatectomy. Two radiologists assigned PI-RADS v2 and {sup 1}H-MRSI scores to index lesions. Statistical analyses used logistic regressions, receiver operating characteristic (ROC) curves, and 2 x 2 tables for diagnostic accuracies. Results: The sensitivity and specificity of {sup 1}H-MRSI and PI-RADS v2 for high-grade prostate cancer (PCa) were 85.7% (57.1%) and 92.9% (100%), and 56% (68.0%) and 24.0% (24.0%). The sensitivity and specificity of {sup 1}H-MRSI and PI-RADS v2 for extra-prostatic extension (EPE) were 64.0% (40%) and 20.0% (48%), and 50.0% (57.1%) and 71.4% (64.3%). The area under the ROC curves (AUC) for prediction of high-grade prostate cancer were 0.65 and 0.61 for PI-RADS v2 and 0.72 and 0.70 when combined with {sup 1}H-MRSI (readers 1 and 2, p = 0.04 and 0.21). For prediction of EPE the AUC were 0.54 and 0.60 for PI-RADS v2 and 0.55 and 0.61 when combined with {sup 1}H-MRSI (p > 0.05). Conclusion: {sup 1}H-MRSI might improve the discrimination of high-grade prostate cancer when combined to PI-RADS v2, particularly for PI-RADS v2 score 4 lesions, but it does not affect the prediction of EPE. (author)

  11. Patterns of Primary Tumor Invasion and Regional Lymph Node Spread Based on Magnetic Resonance Imaging in Early-Stage Nasal NK/T-cell Lymphoma: Implications for Clinical Target Volume Definition and Prognostic Significance

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Run-Ye [Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (China); Liu, Kang [Department of Imaging Diagnosis, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (China); Wang, Wei-Hu; Jin, Jing; Song, Yong-Wen; Wang, Shu-Lian; Liu, Yue-Ping; Ren, Hua; Fang, Hui; Liu, Qing-Feng; Yang, Yong; Chen, Bo; Qi, Shu-Nan; Lu, Ning-Ning; Tang, Yu; Tang, Yuan; Li, Ning [Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (China); Ouyang, Han [Department of Imaging Diagnosis, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (China); Li, Ye-Xiong, E-mail: yexiong12@163.com [Department of Radiation Oncology, National Cancer Center/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing (China)

    2017-01-01

    Purpose: This study aimed to determine the pathways of primary tumor invasion (PTI) and regional lymph node (LN) spread based on magnetic resonance imaging (MRI) in early-stage nasal NK/T-cell lymphoma (NKTCL), to improve clinical target volume (CTV) delineation and evaluate the prognostic value of locoregional extension patterns. Methods and Materials: A total of 105 patients with newly diagnosed early-stage nasal NKTCL who underwent pretreatment MRI were retrospectively reviewed. All patients received radiation therapy with or without chemotherapy. Results: The incidences of PTI and regional LN involvement were 64.7% and 25.7%, respectively. Based on the incidence of PTI, involved sites surrounding the nasal cavity were classified into 3 risk subgroups: high-risk (>20%), intermediate-risk (5%-20%), and low-risk (<5%). The most frequently involved site was the nasopharynx (35.2%), followed by the maxillary (21.9%) and ethmoid (21.9%) sinuses. Local disease and regional LN spread followed an orderly pattern without LN skipping. The retropharyngeal nodes (RPNs) were most frequently involved (19.0%), followed by level II (11.4%). The 5-year overall survival (OS), progression-free survival (PFS), and locoregional control (LRC) rates for all patients were 72.8%, 65.2%, and 90.0%, respectively. The presence of PTI and regional LN involvement based on MRI significantly and negatively affected PFS and OS. Conclusions: Early-stage nasal NKTCL presents with a high incidence of PTI but a relatively low incidence of regional LN spread. Locoregional spread followed an orderly pattern, and PTI and regional LN spread are powerful prognostic factors for poorer survival outcomes. CTV reduction may be feasible for selected patients.

  12. Usefulness of composite methionine-positron emission tomography/3.0-tesla magnetic resonance imaging to detect the localization and extent of early-stage Cushing adenoma.

    Science.gov (United States)

    Ikeda, Hidetoshi; Abe, Takehiko; Watanabe, Kazuo

    2010-04-01

    Fifty to eighty percent of Cushing disease is diagnosed by typical endocrine responses. Recently, the number of diagnoses of Cushing disease without typical Cushing syndrome has been increasing; therefore, improving ways to determine the localization of the adenoma and making an early diagnosis is important. This study was undertaken to determine the present diagnostic accuracy for Cushing microadenoma and to compare the differences in diagnostic accuracy between MR imaging and PET/MR imaging. During the past 3 years the authors analyzed the diagnostic accuracy in a series of 35 patients with Cushing adenoma that was verified by surgical pituitary exploration. All 35 cases of Cushing disease, including 20 cases of "overt" and 15 cases of "preclinical" Cushing disease, were studied. Superconductive MR images (1.5 or 3.0 T) and composite images from FDG-PET or methionine (MET)-PET and 3.0-T MR imaging were compared with the localization of adenomas verified by surgery. The diagnostic accuracy of superconductive MR imaging for detecting the localization of Cushing microadenoma was only 40%. The causes of unsatisfactory results for superconductive MR imaging were false-negative results (10 cases), false-positive results (6 cases), and instances of double pituitary adenomas (3 cases). In contrast, the accuracy of microadenoma localization using MET-PET/3.0-T MR imaging was 100% and that of FDG-PET/3.0-T MR imaging was 73%. Moreover, the adenoma location was better delineated on MET-PET/MR images than on FDG-PET/MR images. There was no significant difference in maximum standard uptake value of adenomas evaluated by MET-PET between preclinical Cushing disease and overt Cushing disease. Composite MET-PET/3.0-T MR imaging is useful for the improvement of the delineation of Cushing microadenoma and offers high-quality detectability for early-stage Cushing adenoma.

  13. Staging of extrahepatic cholangiocarcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Yong Eun; Choi, Jin-Young [Yonsei University College of Medicine, Department of Diagnostic Radiology, Research Institute of Radiological Science, Seoul (Korea); Kim, Myeong-Jin [Yonsei University College of Medicine, Department of Diagnostic Radiology, Research Institute of Radiological Science, Seoul (Korea); Yonsei University College of Medicine, Institute of Gastroenterology, Yonsei (Korea); Yonsei University Health System, Department of Diagnostic Radiology, Seoul (Korea); Park, Young Nyun [Yonsei University College of Medicine, Institute of Gastroenterology, Yonsei (Korea); Yonsei University College of Medicine, Department of Pathology, Yonsei (Korea); Lee, Yoon-Hee [Yonsei University College of Medicine, Department of Pathology, Yonsei (Korea)

    2008-10-15

    Preoperative staging of extrahepatic cholangiocarcinoma is important in determining the best treatment plan. Several classification systems have been suggested to determine the operability and extent of surgery. Longitudinal tumor extent is especially important in extrahepatic cholangiocarcinoma because operative methods differ depending on the tumor extent. The Bismuth-Corlette classification system provides useful information when planning for surgery. However, this classification system is not adequate for selecting surgical candidates. Anatomic variation of the bile duct and gross morphology of the tumor must be considered simultaneously. Lateral spread of the tumor can be evaluated based on the TNM staging provided by American Joint Committee on Cancer (AJCC). However, there is a potential for ambiguity in the distinction of T1 and T2 cancer from one another. In addition, T stage does not necessarily mean invasiveness. Blumgart T staging is helpful for the assessment of resectability with the consideration of nodal status and distant metastasis as suggested by the AJCC cancer staging system. Computed tomography (CT) and magnetic resonance imaging (MRI) are the primary tools used in the assessment of longitudinal and lateral spread of a tumor when determining respectability. Diagnostic laparoscopy and positron emission tomography (PET) may play additional roles in this regard. (orig.)

  14. Staging Mobilities

    DEFF Research Database (Denmark)

    Jensen, Ole B.

    In recent years, the social sciences have taken a “mobilities turn.” There has been a developing realisation that mobilities do not “just happen.” Mobilities are carefully and meticulously designed, planned and staged (from above). However, they are equally importantly acted out, performed and li......, the book asks: what are the physical, social, technical, and cultural conditions to the staging of contemporary urban mobilities?...... that mobility is more than movement between point A and B. It explores how the movement of people, goods, information, and signs influences human understandings of self, other and the built environment. Moving towards a new understanding of the relationship between movement, interaction and environments...

  15. Magnetic compasses in insects

    Science.gov (United States)

    The use of magnetic information for orientation and navigation is a widespread phenomenon in animals. In contrast to navigational systems in vertebrates, our understanding of the mechanisms underlying the insect magnetic perception and use of the information is at an early stage. Some insects use ma...

  16. Treatment Response and Prophylactic Cranial Irradiation Are Prognostic Factors in a Real-life Limited-disease Small-cell Lung Cancer Patient Cohort Comprehensively Staged With Cranial Magnetic Resonance Imaging.

    Science.gov (United States)

    Eze, Chukwuka; Roengvoraphoj, Olarn; Niyazi, Maximilian; Hildebrandt, Guido; Fietkau, Rainer; Belka, Claus; Manapov, Farkhad

    2017-07-01

    Prophylactic cranial irradiation (PCI) has proven to decrease the incidence of brain metastases (BMs), with a modest improvement in survival. The impact of PCI was evaluated in 184 patients treated with chemoradiotherapy. PCI was applied to patients with disease with partial and complete response only when cranial magnetic resonance imaging before and after primary treatment revealed no BMs. Correlation between PCI and overall survival (OS), BM-free survival (BMFS), and time to progression (TTP) was analyzed to describe survival within subgroups. Concurrent and sequential chemoradiotherapy was applied in 71 patients (39%) and 113 patients (61%), respectively. Seventy-one patients (39%) with partial and complete response were treated with PCI. Metachronous BMs were detected in 16 (23%) of 71 patients in the PCI group compared to 42 (37%) of 113 patients in the non-PCI group. Median BMFS in the PCI group was not reached; it was 23.6 months in the non-PCI group. Median OS and TTP were 26 months (range, 19.4-32.6 months) in the PCI group versus 14 months (range, 11.4-16.6 months) in patients without PCI whose disease responded to therapy versus 9 months in patients with disease that did not respond to therapy (P < .0001), and 27 versus 14.5 months (range, 9.0-19.9 months) versus 8.8 months (range, 7.7-9.9 months) (P < .0001) in the PCI group versus those with response without PCI versus those with nonresponse. The effect of PCI was independent of gender. On multivariate analysis, PCI was a variable correlating with OS (hazard ratio = 1.899; 95% confidence interval, 1.370-2.632; P < .0001) and TTP (hazard ratio = 2.164; 95% confidence interval, 1.371-3.415; P = .001) after adjustment for other prognostic factors. In real-life patients comprehensively staged with cranial magnetic resonance imaging, treatment response and PCI strongly correlated with prolonged OS, TTP, and BMFS. Copyright © 2016 Elsevier Inc. All rights reserved.

  17. Radio emission from young supernova remnants - Effects of an inhomogeneous circumstellar medium

    Science.gov (United States)

    Dickel, John R.; Eilek, Jean A.; Jones, Eric M.; Reynolds, Stephen P.

    1989-01-01

    The evolution of young supernova remnants has been modeled using a one-dimensional hydrodynamics code. Rayleigh-Taylor instabilities and the growth of Rayleigh-Taylor fingers have been included in the code. Turbulent dynamo amplification of magnetic fields and both turbulent and shock acceleration of relativistic electrons have been included macroscopically. From this, the distribution of synchrotron luminosity in the remnant has been calculated. It is found that the radio morphology of model remnants expanding into a homogeneous medium does not agree with observations. Expansion into a circumstellar medium with many small cloudlets does produce radio shells which agree with observations. It is suggested that supernova remnants reflect the interaction of ejected matter with a cloudy circumstellar medium.

  18. Reciprocating magnetic refrigerator

    Science.gov (United States)

    Johnson, D. L.

    1985-05-01

    A 4 to 15 K magnetic refrigerator to test as an alternative to the Joule-Thomson circuit as the low temperature stage of a 4 to 300 K closed-cycle refrigerator was developed. The reciprocating magnetic refrigerator consists of two matrices of gadolinium gallium garnet spheres located in tandem on a single piston which alternately moves each matrix into a 7 telsa magnetic field. A separate helium gas circuit is used as the heat exchange mechanism for the low and the high temperature extremes of the magnetic refrigerator. Details of the design and results of the initial refrigerator component tests are presented.

  19. Understanding cancer staging

    Science.gov (United States)

    ... detailed information about the cancer stage. TNM Staging System The most common system for staging cancer in the form of solid tumor is the TNM system. Most providers and cancer centers use it to stage ...

  20. Magnetic structures

    International Nuclear Information System (INIS)

    Oles, A.

    1976-01-01

    Description of progress in magnetic neutron diffraction gives an idea of its comtemporary possibilities. The most typical and interesting magnetic structures are presented. Magnetic structures symmetry is mentioned

  1. Hybrid Fluid/Kinetic Modeling Of Magnetized High Energy Density Plasmas

    Science.gov (United States)

    Hansen, David; Held, Eric; King, Jacob; Stoltz, Peter; Masti, Robert; Srinivasan, Bhuvana

    2017-10-01

    MHD modeling with an equation of state (EOS) of the Rayleigh-Taylor (RT) instabily in Z indicates that it is seeded by the electro-thermal instability. Large thermodynamic drives associated with gradients at the interface between the liner and the coronal regions distort distribution functions and likely lead to non-local transport effects in a plasma which varies from weakly to strongly coupled. In this work, we discuss using effective potential theory along with a Chapman-Ensksog-like (CEL) formalism to develop hybrid fluid/kinetic modeling capabilities for these plasmas. Effective potential theory addresses the role of Coulomb collisions on transport across coupling regimes and the CEL approach bridges the gap between full-blow kinetic simulations and the EOS tables, which only depend locally on density and temperature. Quantitative results on the Spitzer problem across coupling coupling regimes will be presented as a first step. DOE Grant No. DE-SC0016525.

  2. Magnetism and magnetic materials

    International Nuclear Information System (INIS)

    1990-01-01

    It describes the actual status of physics in Brazil concerning the study of magnetism and magnetic materials. It gives an overview of different research groups in Brazil, their needs, as well as the investments needed to improve the area. (A.C.A.S.)

  3. What Happened with Spectrometer Magnet 2B

    Energy Technology Data Exchange (ETDEWEB)

    Green, Michael A

    2010-05-27

    The spectrometer solenoid is supposed to be the first magnets installed in MICE [1]-[4]. This report described what happened during the test of the MICE spectrometer solenoid 2B. First, the report describes the temperatures in the magnet, the cooler top plate and the shield during the run where the magnet quenched at 258 A. During this quench, a lead between the bottom of the HTS leads and the diode bank burned out causing the magnet to quench. Second, three methods for measuring the net heat flow into the cold mass are described. Third, there is a discussion of possible resistive heating in the HTS leads between liquid helium temperature and the copper plate, which is at about 50 K. Fourth, there is a discussion of the measured first stage heat loads in the magnet, when there is no current in the magnet. The first stage heat load calculations are based on knowing the first stage temperatures of the three two-stage pulse tube coolers and the single stage GM cooler. Fifth, the estimated heat load to the first stage when the magnet has current in it is discussed. Sixth, there is a comparison of the stage 1 heat loads in magnet 1A [5], magnet 2A [6], and magnet 2B [7]. Finally there is a discussion of recommended changes for improving the spectrometer solenoids so that the coolers can keep them cold.

  4. Multi-stage depressed collector for small orbit gyrotrons

    Science.gov (United States)

    Singh, Amarjit; Ives, R. Lawrence; Schumacher, Richard V.; Mizuhara, Yosuke M.

    1998-01-01

    A multi-stage depressed collector for receiving energy from a small orbit gyrating electron beam employs a plurality of electrodes at different potentials for sorting the individual electrons on the basis of their total energy level. Magnetic field generating coils, for producing magnetic fields and magnetic iron for magnetic field shaping produce adiabatic and controlled non-adiabatic transitions of the incident electron beam to further facilitate the sorting.

  5. Loess magnetism

    Science.gov (United States)

    Heller, Friedrich; Evans, Michael E.

    Loess is a wind-blown Quaternary silt deposit that blankets vast tracts of land and in places reaches thicknesses in excess of 300 m. Over the last decade it has emerged that certain loess sections have recorded the polarity history of the geomagnetic field and now provide essentially continuous magnetostratigraphic archives covering the last 2-3 m.y. Indeed, it is the chronology provided by the magnetic polarity signature itself that was largely responsible for establishing the timing of the initiation of loess accumulation, particularly in the celebrated Chinese loess plateau, where a starting date close to the Gauss-Matuyama chron boundary (2.6 Ma) is now firmly established. This coincides with a widely documented global climatic shift and accelerated uplift of the Tibetan planteau. Many loess sections contain fossil soils (paleosols) that bear witness to warmer and wetter climatic conditions corresponding to interglacial periods in contrast to the cold, arid environments in which pristine loess accumulated and which correspond to glacial intervals. The resulting sequences of alternating loess and paleosols also manifest themselves magnetically, in this case in terms of susceptibility changes, entirely distinct from the remanence characteristics, which encode the geomagnetic polarity. The susceptibility time series obtained from localities in Alaska and China correlate remarkably well with the oceanic oxygen isotope signal and yield spectral power estimates in agreement with those predicted by the astronomical (Milankovitch) theory of ice ages. Comparisons of susceptibility patterns with corresponding profiles of 10Be concentration in loess allows major changes in rainfall to be estimated. In China, for example data spanning the last 130 kyr (corresponding to oxygen isotope stages 1-5) indicate that paleoprecipitation was almost halved (from ≃540 to ≃310 mm yr-1) as the warm interglacial during which paleosol S1 formed gave way to the following glacial

  6. Comparison of new AJCC staging system with old AJCC staging system in nasopharyngeal carcinoma

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Se Mie; Wu, Hong Gyun; Park, Charn II [College of Medicine, Seoul National Univ., Seoul (Korea, Republic of)

    2000-12-01

    This study was designed to examine the reliability of the new version of the AJCC staging system (1997) of nasopharyngeal carcinoma in comparison with the AJCC staging system of 1992. Between 1983 and 1996, 185 patients with histologically proven nasopharyngeal carcinoma were treated with radiation therapy at the Department of Therapeutic Radiology Seoul National University Hospital. For these patients, AJCC staging system of 1992 was compared with the 1997 version, by reviewing hospital records, computed tomography (CT) and/or magnetic resonance imaging (MRI). 5-year overall survival rates according to the 1992 and 1997 AJCC staging systems were 100%, and 100% at stage I; 100%, and 68.8% at stage ll;61.4%, and 63.8% at stage III; 61.1%, and 63.2% at stage IV. 5-year overall survival rates of each classification showed significant differences between stages (p=0.0049 for the old version, p=0.01 for the new), but no significant difference was found between the staging systems except at stage II. The new AJCC staging system allows staging as reliably as the 1992 version, but the adequacy of the newly modified staging classification should be confirmed by further clinical examination.

  7. Prostate cancer staging

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000397.htm Prostate cancer staging To use the sharing features on this ... trials you may be able to join How Prostate Cancer Staging is Done Initial staging is based on ...

  8. Magnetic refrigerator for hydrogen liquefaction

    Energy Technology Data Exchange (ETDEWEB)

    Matsumoto, K; Kondo, T [Department of Physics, Kanazawa University, Kakuma-machi, Kanazawa 920-1192 (Japan); Yoshioka, S; Kamiya, K; Numazawa, T [Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003 (Japan)], E-mail: kmatsu@kenroku.kanazawa-u.ac.jp

    2009-02-01

    Magnetic refrigeration which is based on the magnetocaloric effect of solids has the potential to achieve high thermal efficiency for hydrogen liquefaction. We have been developing a magnetic refrigerator for hydrogen liquefaction which cools down hydrogen gas from liquid natural gas temperature and liquefies at 20 K. The magnetic liquefaction system consists of two magnetic refrigerators: Carnot magnetic refrigerator (CMR) and active magnetic regenerator (AMR) device. CMR with Carnot cycle succeeded in liquefying hydrogen at 20K. Above liquefaction temperature, a regenerative refrigeration cycle should be necessary to precool hydrogen gas, because adiabatic temperature change of magnetic material is reduced due to a large lattice specific heat of magnetic materials. We have tested an AMR device as the precooling stage. It was confirmed for the first time that AMR cycle worked around 20 K.

  9. Superconducting magnets. B. Superconducting magnet systems in EPR designs

    International Nuclear Information System (INIS)

    Knobloch, A.F.

    1978-01-01

    Tokamak experiments have reached a stage where large scale application of superconductors can be envisaged for machines becoming operational within the next decade. Existing designs for future devices already indicate some of the tasks and problems associated with large superconducting magnet systems. Using this information the coming magnet system requirements are summarized, some design considerations given and in conclusion a brief survey describes already existing Tokamak magnet development programs

  10. Monte Carlo Simulation of Random-Anisotropy Amorphous Magnets

    Science.gov (United States)

    Bondarev, A. V.; Bataronov, I. L.

    2018-01-01

    Using the Monte Carlo method, within the frame of the Heisenberg model, we studies the magnetic properties of amorphous Tb. The relaxation of magnetization of the model of amorphous Tb was studied. We stablished that the relaxation goes in two stages. On the first stage the magnetization sharply decreases by some amount ΔMz , on the second stage the magnetization decreases with time according to the logarithmic law. The possible mechanisms of relaxation is discussed.

  11. Nonlinear collisionless magnetic reconnection

    Science.gov (United States)

    Ottaviani, M.; Porcelli, F.

    1993-12-01

    Collisionless magnetic reconnection in regimes where the mode structure is characterized by global convection cells is found to exhibit a quasiexplosive time behavior in the early nonlinear stage where the fluid displacement is smaller than the equilibrium scale length. This process is accompanied by the formation of a current density sublayer narrower than the skin depth. This sublayer keeps shrinking with time.

  12. Staging N0 oral cancer

    DEFF Research Database (Denmark)

    Thomsen, Jørn Bo; Sørensen, Jens Ahm; Grupe, Peter

    2005-01-01

    PURPOSE: To compare sentinel lymph node biopsy, magnetic resonance imaging (MRI), Doppler ultrasonography, and palpation as staging tools in patients with T1/T2 N0 cancer of the oral cavity. MATERIAL AND METHODS: Forty consecutive patients were enrolled (17 F and 23 M, aged 32-90 years), 24 T1...... and 16 T2 cN0 squamous cell carcinoma of the oral cavity. Palpation was carried out by two observers prior to inclusion. MRI, gray-scale and Doppler ultrasonography were performed. Lymphoscintigraphies were done after peritumoral injections of 99mTc labelled rheniumsulphide nanocolloid, followed......%, but the sensitivity of MRI 36% was low. The specificities were 100%, 85%, and 93%, respectively. By combined sentinel lymph node biopsy and ultrasonography the overall sensitivity could have been 100%. CONCLUSION: Sentinel lymph node biopsy improved staging of patients with small N0 oral cancers. Combined sentinel...

  13. Key issues review: numerical studies of turbulence in stars

    Science.gov (United States)

    Arnett, W. David; Meakin, Casey

    2016-10-01

    Three major problems of single-star astrophysics are convection, magnetic fields and rotation. Numerical simulations of convection in stars now have sufficient resolution to be truly turbulent, with effective Reynolds numbers of \\text{Re}>{{10}4} , and some turbulent boundary layers have been resolved. Implications of these developments are discussed for stellar structure, evolution and explosion as supernovae. Methods for three-dimensional (3D) simulations of stars are compared and discussed for 3D atmospheres, solar rotation, core-collapse and stellar boundary layers. Reynolds-averaged Navier-Stokes (RANS) analysis of the numerical simulations has been shown to provide a novel and quantitative estimate of resolution errors. Present treatments of stellar boundaries require revision, even for early burning stages (e.g. for mixing regions during He-burning). As stellar core-collapse is approached, asymmetry and fluctuations grow, rendering spherically symmetric models of progenitors more unrealistic. Numerical resolution of several different types of three-dimensional (3D) stellar simulations are compared; it is suggested that core-collapse simulations may be under-resolved. The Rayleigh-Taylor instability in explosions has a deep connection to convection, for which the abundance structure in supernova remnants may provide evidence.

  14. The physics of fast Z pinches

    International Nuclear Information System (INIS)

    Ryutov, D.D.; Derzon, M.S.; Matzen, M.K.

    1998-07-01

    The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizes the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z-pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 52 figures and nearly 300 references

  15. The physics of fast Z pinches

    Energy Technology Data Exchange (ETDEWEB)

    Ryutov, D.D. [Lawrence Livermore National Lab., CA (United States); Derzon, M.S.; Matzen, M.K. [Sandia National Labs., Albuquerque, NM (United States)

    1998-07-01

    The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizes the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z-pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 52 figures and nearly 300 references.

  16. The Physics of Fast Z Pinches

    Energy Technology Data Exchange (ETDEWEB)

    RYUTOV,D.D.; DERZON,MARK S.; MATZEN,M. KEITH

    1999-10-25

    The spectacular progress made during the last few years in reaching high energy densities in fast implosions of annular current sheaths (fast Z pinches) opens new possibilities for a broad spectrum of experiments, from x-ray generation to controlled thermonuclear fusion and astrophysics. Presently Z pinches are the most intense laboratory X ray sources (1.8 MJ in 5 ns from a volume 2 mm in diameter and 2 cm tall). Powers in excess of 200 TW have been obtained. This warrants summarizing the present knowledge of physics that governs the behavior of radiating current-carrying plasma in fast Z pinches. This survey covers essentially all aspects of the physics of fast Z pinches: initiation, instabilities of the early stage, magnetic Rayleigh-Taylor instability in the implosion phase, formation of a transient quasi-equilibrium near the stagnation point, and rebound. Considerable attention is paid to the analysis of hydrodynamic instabilities governing the implosion symmetry. Possible ways of mitigating these instabilities are discussed. Non-magnetohydrodynamic effects (anomalous resistivity, generation of particle beams, etc.) are summarized. Various applications of fast Z pinches are briefly described. Scaling laws governing development of more powerful Z pinches are presented. The survey contains 36 figures and more than 300 references.

  17. Between Stage and Screen

    NARCIS (Netherlands)

    Tornqvist, Egil

    1996-01-01

    Ingmar Bergman is worldwide known as a film and stage director. Yet no-one has attempted to compare his stage and screen activities. In Between stage and screen Egil Tornqvist examines formal and thematical correspondences and differences between a number of Bergman's stage, screen, and radio

  18. Magnetism, Nanosized Magnetic Materials

    Science.gov (United States)

    Miller, Joel S.; Drillon, Marc

    2002-01-01

    Magnetic behaviour, once thought to be mature, has gained a new momentum as it is being expanded by contributions from molecular chemistry, materials sciences to solid state physics. The spectrum spans molecule-based - organic, inorganic, and hybrid - compounds, metallic materials as well as their oxides forming, for example, thin films, nanoparticles, nanowires. New phenomena are explored that open promising perspectives for commercially applied "smart" materials. As a depository of contemporary knowledge on key topics related to magnetism, this open series of volumes provides a much-needed comprehensive overview of this growing interdisciplinary field. The topical reviews are written by the foremost scientists in the area, and the trends and recent advances are explained in a clear and detailed manner with a focus on the correlations between electronic structure and magnetic properties. The balance between theory and experiment within this series will guide advanced students and specialists in evaluating experimental observations and will serve as a basis for the design of new magnetic materials. This is a unique reference work, indispensable for everyone concerned with the phenomena of magnetism!

  19. Internal structure of magnetic endosomes.

    Science.gov (United States)

    Rivière, C; Wilhelm, C; Cousin, F; Dupuis, V; Gazeau, F; Perzynski, R

    2007-01-01

    The internal structure of biological vesicles filled with magnetic nanoparticles is investigated using the following complementary analyses: electronic transmission microscopy, dynamic probing by magneto-optical birefringence and structural probing by Small Angle Neutron Scattering (SANS). These magnetic vesicles are magnetic endosomes obtained via a non-specific interaction between cells and anionic magnetic iron oxide nanoparticles. Thanks to a magnetic purification process, they are probed at two different stages of their formation within HeLa cells: (i) adsorption of nanoparticles onto the cellular membrane and (ii) their subsequent internalisation within endosomes. Differences in the microenvironment of the magnetic nanoparticles at those two different stages are highlighted here. The dynamics of magnetic nanoparticles adsorbed onto cellular membranes and confined within endosomes is respectively 3 and 5 orders of magnitude slower than for isolated magnetic nanoparticles in aqueous media. Interestingly, SANS experiments show that magnetic endosomes have an internal structure close to decorated vesicles, with magnetic nanoparticles locally decorating the endosome membrane, inside their inner-sphere. These results, important for future biomedical applications, suggest that multiple fusions of decorated vesicles are the biological processes underlying the endocytosis of that kind of nanometric materials.

  20. Internal structure of magnetic endosomes

    Science.gov (United States)

    Rivière, C.; Wilhelm, C.; Cousin, F.; Dupuis, V.; Gazeau, F.; Perzynski, R.

    2007-01-01

    The internal structure of biological vesicles filled with magnetic nanoparticles is investigated using the following complementary analyses: electronic transmission microscopy, dynamic probing by magneto-optical birefringence and structural probing by Small Angle Neutron Scattering (SANS). These magnetic vesicles are magnetic endosomes obtained via a non-specific interaction between cells and anionic magnetic iron oxide nanoparticles. Thanks to a magnetic purification process, they are probed at two different stages of their formation within HeLa cells: (i) adsorption of nanoparticles onto the cellular membrane and (ii) their subsequent internalisation within endosomes. Differences in the microenvironment of the magnetic nanoparticles at those two different stages are highlighted here. The dynamics of magnetic nanoparticles adsorbed onto cellular membranes and confined within endosomes is respectively 3 and 5 orders of magnitude slower than for isolated magnetic nanoparticles in aqueous media. Interestingly, SANS experiments show that magnetic endosomes have an internal structure close to decorated vesicles, with magnetic nanoparticles locally decorating the endosome membrane, inside their inner-sphere. These results, important for future biomedical applications, suggest that multiple fusions of decorated vesicles are the biological processes underlying the endocytosis of that kind of nanometric materials.

  1. Magnetic power piston fluid compressor

    Science.gov (United States)

    Gasser, Max G. (Inventor)

    1994-01-01

    A compressor with no moving parts in the traditional sense having a housing having an inlet end allowing a low pressure fluid to enter and an outlet end allowing a high pressure fluid to exit is described. Within the compressor housing is at least one compression stage to increase the pressure of the fluid within the housing. The compression stage has a quantity of magnetic powder within the housing, is supported by a screen that allows passage of the fluid, and a coil for selectively providing a magnetic field across the magnetic powder such that when the magnetic field is not present the individual particles of the powder are separated allowing the fluid to flow through the powder and when the magnetic field is present the individual particles of the powder pack together causing the powder mass to expand preventing the fluid from flowing through the powder and causing a pressure pulse to compress the fluid.

  2. Magnetic Levitation.

    Science.gov (United States)

    Rossing, Thomas D.; Hull, John R.

    1991-01-01

    Discusses the principles of magnetic levitation presented in the physics classroom and applied to transportation systems. Topics discussed include three classroom demonstrations to illustrate magnetic levitation, the concept of eddy currents, lift and drag forces on a moving magnet, magnetic levitation vehicles, levitation with permanent magnets…

  3. Magnetic properties

    Indian Academy of Sciences (India)

    Unknown

    netic moments of the particles, i.e. Zeeman energy, µH, where µ is the magnetic moment of the particle and H .... the domain magnetization of particle. Here, we have assumed a log-normal distribution function, P(D), for ... Effect of texturing field on a magnetically textured fluid magnetization for (a) (HT || H) and (b) (HT ⊥ H) ...

  4. Magnetic Spinner

    Science.gov (United States)

    Ouseph, P. J.

    2006-01-01

    A science toy sometimes called the "magnetic spinner" is an interesting class demonstration to illustrate the principles of magnetic levitation. It can also be used to demonstrate Faraday's law and a horizontally suspended physical pendulum. The levitated part contains two circular magnets encased in a plastic housing. Each magnet stays…

  5. Breast cancer staging

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/patientinstructions/000911.htm Breast cancer staging To use the sharing features on this ... Once your health care team knows you have breast cancer , they will do more tests to stage it. ...

  6. Seven Stages of Alzheimer's

    Science.gov (United States)

    ... Dementias . Learn more: Daily Care and Behaviors Severe Alzheimer's disease (late-stage) Get support Late-stage care decisions can be some of the hardest families face. Connect with other caregivers who have been through the process on our ...

  7. Stages of Adolescence

    Science.gov (United States)

    ... Español Text Size Email Print Share Stages of Adolescence Page Content Article Body Adolescence, these years from puberty to adulthood, may be roughly divided into three stages: early adolescence, generally ages eleven to fourteen; middle adolescence, ages ...

  8. Beyond Erikson's Eight Stages.

    Science.gov (United States)

    Whitney, Ruth

    1979-01-01

    Erik Erikson has described eight stages of the healthy personality. This essay offers a revised version of the eight stages. Although most individuals develop through the eight stages, each is personally unique because patterns of fluctuation between safety and growth differ from one individual to another. (Author)

  9. Cervical Cancer Stage IIIA

    Science.gov (United States)

    ... hyphen, e.g. -historical Searches are case-insensitive Cervical Cancer Stage IIIA Add to My Pictures View /Download : ... 1275x1275 View Download Large: 2550x2550 View Download Title: Cervical Cancer Stage IIIA Description: Stage IIIA cervical cancer; drawing ...

  10. Cervical Cancer Stage IVA

    Science.gov (United States)

    ... hyphen, e.g. -historical Searches are case-insensitive Cervical Cancer Stage IVA Add to My Pictures View /Download : ... 1575x1200 View Download Large: 3150x2400 View Download Title: Cervical Cancer Stage IVA Description: Stage IVA cervical cancer; drawing ...

  11. Cervical Cancer Stage IVB

    Science.gov (United States)

    ... hyphen, e.g. -historical Searches are case-insensitive Cervical Cancer Stage IVB Add to My Pictures View /Download : ... 1200x1305 View Download Large: 2400x2610 View Download Title: Cervical Cancer Stage IVB Description: Stage IVB cervical cancer; drawing ...

  12. Cervical Cancer Stage IIIB

    Science.gov (United States)

    ... hyphen, e.g. -historical Searches are case-insensitive Cervical Cancer Stage IIIB Add to My Pictures View /Download : ... 1425x1326 View Download Large: 2850x2651 View Download Title: Cervical Cancer Stage IIIB Description: Stage IIIB cervical cancer; drawing ...

  13. Cervical Cancer Stage IB

    Science.gov (United States)

    ... hyphen, e.g. -historical Searches are case-insensitive Cervical Cancer Stage IB Add to My Pictures View /Download : ... 1613x1200 View Download Large: 3225x2400 View Download Title: Cervical Cancer Stage IB Description: Stage IB1 and IB2 cervical ...

  14. Cervical Cancer Stage IA

    Science.gov (United States)

    ... historical Searches are case-insensitive Cervical Cancer Stage IA Add to My Pictures View /Download : Small: 720x576 ... Large: 3000x2400 View Download Title: Cervical Cancer Stage IA Description: Stage IA1 and IA2 cervical cancer; drawing ...

  15. Magnetic positioner having a single moving part

    Energy Technology Data Exchange (ETDEWEB)

    Trumper, David L. (Plaistow, NH); Kim, Won-Jong (Cambridge, MA)

    1999-01-01

    A magnetic positioner is provided which is capable of providing long travel in two dimension and short travel in the remaining four dimensions. The positioner has a movable stage and a stator oriented adjacent and substantially parallel to this stage. At least three sets of first magnetic elements, which for preferred embodiments are winding sets capable of generating forces in two directions, are on the portion of the stator adjacent to the stage at any given time, and at least two second magnetic elements, which are magnet arrays for the preferred embodiment, are on the stage adjacent to the stator. At least one of the second magnetic elements overlaps multiple first magnetic elements for all positions of the stage relative to the stator, with one magnet overlapping multiple windings for one preferred embodiment of the invention and two magnets on the stage overlapping multiple windings on the stator for a second embodiment. The windings form a linear motor providing forces in both a corresponding long travel dimension and in a dimension perpendicular to both long travel dimensions.

  16. Magnetic positioner having a single moving part

    Energy Technology Data Exchange (ETDEWEB)

    Trumper, D.L.; Kim, W.J.

    1999-12-21

    A magnetic positioner is provided which is capable of providing long travel in two dimension and short travel in the remaining four dimensions. The positioner has a movable stage and a stator oriented adjacent and substantially parallel to this stage. At least three sets of first magnetic elements, which for preferred embodiments are winding sets capable of generating forces in two directions, are on the portion of the stator adjacent to the stage at any given time, and at least two second magnetic elements, which are magnet arrays for the preferred embodiment, are on the stage adjacent to the stator. At least one of the second magnetic elements overlaps multiple first magnetic elements for all positions of the stage relative to the stator, with one magnet overlapping multiple windings for one preferred embodiment of the invention and two magnets on the stage overlapping multiple windings on the stator for a second embodiment. The windings form a linear motor providing forces in both a corresponding long travel dimension and in a dimension perpendicular to both long travel dimensions.

  17. Cetuximab, Cisplatin, and Radiation Therapy in Treating Patients With Stage IB, Stage II, Stage III, or Stage IVA Cervical Cancer

    Science.gov (United States)

    2014-12-29

    Cervical Adenocarcinoma; Cervical Adenosquamous Carcinoma; Cervical Small Cell Carcinoma; Cervical Squamous Cell Carcinoma; Stage IB Cervical Cancer; Stage IIA Cervical Cancer; Stage IIB Cervical Cancer; Stage III Cervical Cancer; Stage IVA Cervical Cancer

  18. Staging of Cervical Lymph Nodes in Oral Squamous Cell Carcinoma

    DEFF Research Database (Denmark)

    Norling, Rikke; Buron, Birgitte Marie Due; Therkildsen, Marianne Hamilton

    2014-01-01

    INTRODUCTION: Clinical staging of patients with oral squamous cell carcinoma (OSCC) is crucial for the choice of treatment. Computed tomography (CT) and/or magnetic resonance imaging (MRI) are typically recommended and used for staging of the cervical lymph nodes (LNs). Although ultrasonography (US...

  19. Chemically induced breast tumors in rats are detectable in early stages by contrast enhanced magnetic resonance imaging but not by changes in the acute-phase reactants in serum.

    Science.gov (United States)

    Golbabapour, Shahram; Pang, Wei Wei; George, John; Pasupati, Thanikachalam; Abdul-Rahman, Puteri Shafinaz; Hashim, Onn Haji

    2011-02-07

    The present study was undertaken to develop a rat model for monitoring the early development of breast cancer. Twelve female rats were divided into two groups of six rats that were either treated with N-methyl-N-nitrosourea to induce breast cancer or with bacterial lipopolysaccharide to induce inflammation. Serum samples taken from the rats prior to the treatment were used as controls. By the 14th week, presence of the tumor was detectable by contrast enhanced magnetic resonance imaging and confirmed by histopathology. When the serum proteins of the rats were examined by 2-dimensional electrophoresis (2-DE), no difference could be detected in the profiles of all proteins before and 18 weeks after administration of N-methyl-N-nitrosourea. However, higher expression of alpha-1B glycoprotein was detectable by 2-DE in serum samples of rats at the 18th week post-treatment with lipopolysaccharide.

  20. Chemically Induced Breast Tumors in Rats Are Detectable in Early Stages by Contrast Enhanced Magnetic Resonance Imaging but Not by Changes in the Acute-Phase Reactants in Serum

    Directory of Open Access Journals (Sweden)

    Onn Haji Hashim

    2011-02-01

    Full Text Available The present study was undertaken to develop a rat model for monitoring the early development of breast cancer. Twelve female rats were divided into two groups of six rats that were either treated with N-methyl-N-nitrosourea to induce breast cancer or with bacterial lipopolysaccharide to induce inflammation. Serum samples taken from the rats prior to the treatment were used as controls. By the 14th week, presence of the tumor was detectable by contrast enhanced magnetic resonance imaging and confirmed by histopathology. When the serum proteins of the rats were examined by 2-dimensional electrophoresis (2-DE, no difference could be detected in the profiles of all proteins before and 18 weeks after administration of N-methyl-N-nitrosourea. However, higher expression of alpha-1B glycoprotein was detectable by 2-DE in serum samples of rats at the 18th week post-treatment with lipopolysaccharide.

  1. Active Magnetic Regenerative Liquefier

    Energy Technology Data Exchange (ETDEWEB)

    Barclay, John A. [Heracles Energy Corporation d.b.a. Prometheus Energy, Washington, DC (United States); Oseen-Send, Kathryn [Heracles Energy Corporation d.b.a. Prometheus Energy, Washington, DC (United States); Ferguson, Luke [Heracles Energy Corporation d.b.a. Prometheus Energy, Washington, DC (United States); Pouresfandiary, Jamshid [Heracles Energy Corporation d.b.a. Prometheus Energy, Washington, DC (United States); Cousins, Anand [Heracles Energy Corporation d.b.a. Prometheus Energy, Washington, DC (United States); Ralph, Heather [Heracles Energy Corporation d.b.a. Prometheus Energy, Washington, DC (United States); Hampto, Tom [Heracles Energy Corporation d.b.a. Prometheus Energy, Washington, DC (United States)

    2016-01-12

    This final report for the DOE Project entitled Active Magnetic Regenerative Liquefier (AMRL) funded under Grant DE-FG36-08GO18064 to Heracles Energy Corporation d.b.a. Prometheus Energy (Heracles/Prometheus) describes an active magnetic regenerative refrigerator (AMRR) prototype designed and built during the period from July 2008 through May 2011. The primary goal of this project was to make significant technical advances toward highly efficient liquefaction of hydrogen. Conventional hydrogen liquefiers at any scale have a maximum FOM of ~0.35 due primarily to the intrinsic difficulty of rapid, efficient compression of either hydrogen or helium working gases. Numerical simulation modeling of high performance AMRL designs indicates certain designs have promise to increase thermodynamic efficiency from a FOM of ~0.35 toward ~0.5 to ~0.6. The technical approach was the use of solid magnetic working refrigerants cycled in and out of high magnetic fields to build an efficient active regenerative magnetic refrigeration module providing cooling power for AMRL. A single-stage reciprocating AMRR with a design temperature span from ~290 K to ~120 K was built and tested with dual magnetic regenerators moving in and out of the conductively-cooled superconducting magnet subsystem. The heat transfer fluid (helium) was coupled to the process stream (refrigeration/liquefaction load) via high performance heat exchangers. In order to maximize AMRR efficiency a helium bypass loop with adjustable flow was incorporated in the design because the thermal mass of magnetic refrigerants is higher in low magnetic field than in high magnetic field. Heracles/Prometheus designed experiments to measure AMRR performance under a variety of different operational parameters such as cycle frequency, magnetic field strength, heat transfer fluid flow rate, amount of bypass flow of the heat transfer fluid while measuring work input, temperature span, cooling capability as a function of cold temperature

  2. Magnetic Fields

    OpenAIRE

    Schöller, Markus; Hubrig, Swetlana

    2015-01-01

    In this chapter, we give a brief introduction into the use of the Zeeman effect in astronomy and the general detection of magnetic fields in stars, concentrating on the use of FORS2 for longitudinal magnetic field measurements.

  3. Superconducting Magnets

    CERN Multimedia

    CERN. Geneva

    2008-01-01

    Starting from the beam requirements for accelerator magnets, we will outline the main issues and the physical limitations for producing strong and pure magnetic fields with superconductors. The seminar will mainly focus on the magnets for the accelerator, and give some hints on the magnets for the experiments. Prerequisite knowledge: Basic knowledge of Maxwell equations, and linear optics for particle accelerators (FODO cell, beta functions).

  4. Magnetic Nanostructures

    OpenAIRE

    Bennemann, K. H.

    2010-01-01

    Characteristic results of magnetism in small particles and thin films are presented. As a consequence of the reduced atomic coordination in small clusters and thin films the electronic states and density of states modify. Thus magnetic moments and magnetization are affected. In tunnel junctions interplay of magnetism, spin currents and superconductivity are of particular interest. Results are given for single transition metal clusters, cluster ensembles, thin films and tunnel systems. Interes...

  5. Magnetic strings

    International Nuclear Information System (INIS)

    Chaves, Max

    2006-01-01

    The conception of the magnetic string is presented as an infinitely thin bundle of magnetic flux lines. The magnetic strings are surrounded by a film of current that rotates around them, and are a solution of Maxwell's equations. The magnetic potential contains a line singularity, and its stability can be established topologically. A few comments are added on the possibility that they may exist at a cosmological scale as relics of the Big Bang. (author) [es

  6. Magnetic Materials

    Science.gov (United States)

    Spaldin, Nicola A.

    2003-04-01

    Magnetic materials are the foundation of multi-billion dollar industries and the focus of intensive research across many disciplines. This book covers the fundamentals, basic theories and applications of magnetism and conventional magnetic materials. Based on a lecture course given by Nicola Spaldin in the Materials Department at University of California, Santa Barbara, the book is ideal for a one- semester course in magnetic materials. It contains numerous homework problems and solutions.

  7. Turbine stage model

    International Nuclear Information System (INIS)

    Kazantsev, A.A.

    2009-01-01

    A model of turbine stage for calculations of NPP turbine department dynamics in real time was developed. The simulation results were compared with manufacturer calculations for NPP low-speed and fast turbines. The comparison results have shown that the model is valid for real time simulation of all modes of turbines operation. The model allows calculating turbine stage parameters with 1% accuracy. It was shown that the developed turbine stage model meets the accuracy requirements if the data of turbine blades setting angles for all turbine stages are available [ru

  8. Amorphous magnetism

    International Nuclear Information System (INIS)

    Rechenberg, H.R.

    1984-01-01

    The consequences of disorder on magnetic properties of solids are examined. In this context the word 'disorder' is not synonimous of structural amorphicity; chemical disorder can be achieved e.g. by randomly diffusing magnetic atoms on a nonmagnetic crystalline lattice. The name Amorphous Magnetism must be taken in a broad sense. (Author) [pt

  9. Superconducting magnets

    International Nuclear Information System (INIS)

    1994-08-01

    This report discusses the following topics on superconducting magnets: D19B and -C: The next steps for a record-setting magnet; D20: The push beyond 10 T: Beyond D20: Speculations on the 16-T regime; other advanced magnets for accelerators; spinoff applications; APC materials development; cable and cabling-machine development; and high-T c superconductor at low temperature

  10. Magnetic Reconnection

    NARCIS (Netherlands)

    Schep, T. J.

    1994-01-01

    This lecture deals with the concept of magnetic field lines and with the conservation of magnetic flux. In high temperature fusion devices like tokamaks flux conservation can be violated and reconnection can occur at closed magnetic field lines. Reconnection processes lead to changes in the global

  11. [Application value of magnetic compression anastomosis in digestive tract reconstruction].

    Science.gov (United States)

    Du, Xilin; Fan, Chao; Zhang, Hongke; Lu, Jianguo

    2014-05-01

    Magnetic compression anastomosis can compress tissues together and restore the continuity. Magnetic compression anastomosis mainly experienced three stages: magnetic ring, magnetic ring and column, and smart self-assembling magnets for endoscopy (SAMSEN). Nowadays, the magnetic compression anastomosis has been applied in vascular and different digestive tract surgeries, especially for complex surgery, such as anastomotic stenosis of biliary ducts after liver transplantation or congenital esophageal stenosis. Although only case reports are available at present, the advantages of the magnetic compression anastomosis includes lower cost, simplicity, individualization, good efficacy, safety, and minimally invasiveness. We are building a better technical platform to make magnetic compression anastomosis more advanced and popularized.

  12. Staging of cutaneous melanoma

    NARCIS (Netherlands)

    P. Mohr (P.); A.M.M. Eggermont (Alexander); A. Hauschild (Axel); A. Buzaid (A.)

    2009-01-01

    textabstractThe American Joint Committee on Cancer (AJCC) staging of cutaneous melanoma is a continuously evolving system. The identification of increasingly more accurate prognostic factors has led to major changes in melanoma staging over the years, and the current system described in this review

  13. Generation of superDreicer electric fields in the solar chromosphere

    Science.gov (United States)

    Zaitsev, V. V.; Kronshtadtov, P. V.; Stepanov, A. V.

    2016-12-01

    The electric field generation at the front of the current pulse, which originates in a coronal magnetic loop owing to the development of the Rayleigh-Taylor magnetic instability at loop footpoints, has been considered. During the τA ≈ l/V A ≈ 5-25 s time (where l is the plasma plume height entering a magnetic loop as a result of the Rayleigh-Taylor instability), a disturbance related to the magnetic field tension B ϕ( r,t), "escapes" the instability region with the Alfvén velocity in this case. As a result, an electric current pulse Iz( z - V A t), at the front of which an induction magnetic field E z, which is directed along the magnetic tube axis and can therefore accelerate particles, starts propagating along a magnetic loop with a characteristic scale of Δξ ≈ l. In the case of sufficiently large currents, when B ϕ 2/8π > p, an electric current pulse propagates nonlinearly, and a relatively large longitudinal electric field originates E z ≈ 2 I z 3 V A/ c 4a2Bz 2l, which can be larger than the Dreicer field, depending on the electric current value.

  14. Preoperative staging of rectal cancer.

    Science.gov (United States)

    Smith, Neil; Brown, Gina

    2008-01-01

    Detailed preoperative staging using high resolution magnetic resonance imaging (MRI) enables the selection of patients that require preoperative therapy for tumour regression. This information can be used to instigate neoadjuvant therapy in those patients with poor prognostic features prior to disturbing the tumour bed and potentially disseminating disease. The design of trials incorporating MR assessment of prognostic factors prior to therapy has been found to be of value in assessing treatment modalities and outcomes that are targeted to these preoperative prognostic subgroups and in providing a quantifiable assessment of the efficacy of particular chemoradiation treatment protocols by comparing pre-treatment MR staging with post therapy histology assessment. At present, we are focused on achieving clear surgical margins of excision (CRM) to avoid local recurrence. We recommend that all patients with rectal cancer should undergo pre-operative MRI staging. Of these, about half will have good prognosis features (T1-T3b, N0, EMVI negative, CRM clear) and may safely undergo primary total mesorectal excision. Of the remainder, those with threatened or involved margins will certainly benefit from pre-operative chemoradiotherapy with the aim of downstaging to permit safe surgical excision. In the future, our ability to recognise features predicting distant failure, such as extramural vascular invasion (EMVI) may be used to stratify patients for neo-adjuvant systemic chemotherapy in an effort to prevent distant relapse. The optimal pre-operative treatment regimes for these patients (radiotherapy alone, systemic chemotherapy alone or combination chemo-radiotherapy) is the subject of current and future trials.

  15. Staging for vulvar cancer.

    Science.gov (United States)

    Hacker, Neville F; Barlow, Ellen L

    2015-08-01

    Vulvar cancer has been staged by the International Federation of Gynaecology and Obstetrics (FIGO) since 1969, and the original staging system was based on clinical findings only. This system provided a very good spread of prognostic groupings. Because vulvar cancer is virtually always treated surgically, the status of the lymph nodes is the most important prognostic factor and this can only be determined with certainty by histological examination of resected lymph nodes, FIGO introduced a surgical staging system in 1988. This was modified in 1994 to include a category of microinvasive vulvar cancer (stage IA), because such patients have virtually no risk of lymph node metastases. This system did not give a reasonably even spread of prognostic groupings. In addition, patients with stage III disease were shown to be a heterogeneous group prognostically, and the number of positive nodes and the morphology of those nodes were not taken into account. A new surgical staging system for vulvar cancer was introduced by FIGO in 2009. Initial retrospective analyses have suggested that this new staging system has overcome the major deficiencies in the 1994 system. Crown Copyright © 2015. Published by Elsevier Ltd. All rights reserved.

  16. Staged bilateral carotid endarterectomy

    DEFF Research Database (Denmark)

    Schroeder, T; Sillesen, H; Engell, Hans Christian

    1986-01-01

    In a series of 56 staged bilateral carotid endarterectomies, new neurologic symptoms developed in 5% and 20% following the first and second procedure, respectively. All complications were transient or minor. The incidence of postendarterectomy hypertension was significantly higher following...... the second procedure, when operations were staged less than 3 weeks apart. A correlation between these hypertensive episodes and the occurrence of new neurologic symptoms could not be shown. However, as this correlation has been proved in several other reports, bilateral carotid endarterectomy is advised...... to be staged at least 3 weeks apart. In addition, a conservative attitude towards contralateral asymptomatic lesions is proposed....

  17. Staging of lung cancer.

    Science.gov (United States)

    de Groot, Patricia M; Carter, Brett W; Betancourt Cuellar, Sonia L; Erasmus, Jeremy J

    2015-06-01

    Primary lung cancer is the leading cause of cancer mortality in the world. Thorough clinical staging of patients with lung cancer is important, because therapeutic options and management are to a considerable degree dependent on stage at presentation. Radiologic imaging is an essential component of clinical staging, including chest radiography in some cases, computed tomography, MRI, and PET. Multiplanar imaging modalities allow assessment of features that are important for surgical, oncologic, and radiation therapy planning, including size of the primary tumor, location and relationship to normal anatomic structures in the thorax, and existence of nodal and/or metastatic disease. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Staging Mobilities / Designing Mobilities

    DEFF Research Database (Denmark)

    Jensen, Ole B.

    2015-01-01

    In recent years, urban research has taken a ‘mobilities turn’. There has been a developing realisation that mobilities do not ‘just happen.’ Mobilities are carefully and meticulously designed, planned and staged (from above). However, they are equally importantly acted out, performed and lived...... asks: what are the physical, social, technical, and cultural conditions to the staging of contemporary urban mobilities? The theoretical framing in the Staging mobilities book is applied to four in-depth cases in the accompanying volume Designing mobilities.This book explore how places, sites...

  19. Protein purification using magnetic adsorbent particles

    DEFF Research Database (Denmark)

    Franzreb, M; Siemann-Herzberg, M.; Hobley, Timothy John

    2006-01-01

    The application of functionalised magnetic adsorbent particles in combination with magnetic separation techniques has received considerable attention in recent years. The magnetically responsive nature of such adsorbent particles permits their selective manipulation and separation in the presence...... of other suspended solids. Thus, it becomes possible to magnetically separate selected target species directly out of crude biological process liquors (e.g. fermentation broths, cell disruptates, plasma, milk, whey and plant extracts) simply by binding them on magnetic adsorbents before application...... of a magnetic field. By using magnetic separation in this way, the several stages of sample pretreatment (especially centrifugation, filtration and membrane separation) that are normally necessary to condition an extract before its application on packed bed chromatography columns, may be eliminated. Magnetic...

  20. Calculations of the R-T liner instabilities on the base of the Baker-Freeman nonlinear model

    International Nuclear Information System (INIS)

    Loskutov, V.V.; Luchinskij, A.V.

    1995-01-01

    Nonlinear model Rayleigh-Taylor instabilities, suggested by Baker and Freeman to study instabilities in targets for inertial controlled thermonuclear fusion, was used for investigation of similar problems, arising at liner implosion. The model, as applied to the problem of liner acceleration by inherent magnetic field, is described. The correlation of the given model with known results of two-dimensional MHD-calculations, is presented. The problem of development of linear R-T-instability, when transmitting 15-20 MA current pulse with 200 ns edge, was considered. 8 refs., 5 figs

  1. Compression of toroidal plasma by imploding plasma-liner

    International Nuclear Information System (INIS)

    Ikuta, Kazunari.

    1979-07-01

    A new concept of compressing a plasma in a closed magnetic configuration by a version of liner implosion flux compression technique is considered. The liner consists of a dense plasma cylinder, i.e. the plasma-liner. Maximum compression ratio of toroidal plasma is determined just by the initial density ratio of the toroidal plasma to the liner plasma because of the Rayleigh-Taylor instability. A start-up senario of plasma-liner is also proposed with a possible application of this concept to the creation of a burning plasma in reversed field configurations, i.e. burning plasma vortex. (author)

  2. Magnetic Hysteresis

    CERN Document Server

    Della Torre, Edward

    2000-01-01

    Understanding magnetic hysteresis is vitally important to the development of the science of magnetism as a whole and to the advancement of practical magnetic device applications. Magnetic Hysteresis, by acclaimed expert Edward Della Torre, presents a clear explanation of the connection between physical principles and phenomenological hysteresis. This comprehensive book offers a lucid analysis that enables the reader to save valuable time by reducing trial-and-error design. Dr. Della Torre uses physical principles to modify Preisach modeling and to describe the complex behavior of magnetic media. While Pretsach modeling is a useful mathematical tool, its congruency and deletion properties present limitations to accurate descriptions of magnetic materials. Step-by-step, this book describes the modifications that can overcome these limitations. Special attention is given to the use of feedback around a Preisach transducer to remove the congruency restriction, and to the use of accommodation and aftereffect model...

  3. Magnetic switching

    International Nuclear Information System (INIS)

    Kirbie, H.C.

    1989-01-01

    Magnetic switching is a pulse compression technique that uses a saturable inductor (reactor) to pass pulses of energy between two capacitors. A high degree of pulse compression can be achieved in a network when several of these simple, magnetically switched circuits are connected in series. Individual inductors are designed to saturate in cascade as a pulse moves along the network. The technique is particularly useful when a single-pulse network must be very reliable or when a multi-pulse network must operate at a high pulse repetition frequency (PRF). Today, magnetic switches trigger spark gaps, sharpen the risetimes of high energy pulses, power large lasers, and drive high PRF linear induction accelerators. This paper will describe the technique of magnetic pulse compression using simple networks and design equations. A brief review of modern magnetic materials and of their role in magnetic switch design will be presented. 12 refs., 8 figs

  4. Planetary Magnetism

    Science.gov (United States)

    Connerney, J. E. P.

    2007-01-01

    The chapter on Planetary Magnetism by Connerney describes the magnetic fields of the planets, from Mercury to Neptune, including the large satellites (Moon, Ganymede) that have or once had active dynamos. The chapter describes the spacecraft missions and observations that, along with select remote observations, form the basis of our knowledge of planetary magnetic fields. Connerney describes the methods of analysis used to characterize planetary magnetic fields, and the models used to represent the main field (due to dynamo action in the planet's interior) and/or remnant magnetic fields locked in the planet's crust, where appropriate. These observations provide valuable insights into dynamo generation of magnetic fields, the structure and composition of planetary interiors, and the evolution of planets.

  5. Stages of Colon Cancer

    Science.gov (United States)

    ... types of surgery : Local excision or simple polypectomy . Resection and anastomosis . This is done when the tumor is too ... stage I colon cancer usually includes the following: Resection and anastomosis . Use our clinical trial search to find NCI- ...

  6. Stages of Labor

    Science.gov (United States)

    ... Moms Need Blog News & Media News Videos Mission stories Ambassadors Spotlights Tools & Resources Frequently asked media questions ... can be born. This stage can last as short as 20 minutes or as long as several ...

  7. Multiple Stages 2

    DEFF Research Database (Denmark)

    Andreasen, John

    Multiple stages 2: theatrical futures, set design, community plays, cultural capitals, democracy & drama, WWII dramas, performance on adoption, promenade about emigration, qualities in political theatre, performance analysis, dramaturgical education, Toulmin Variations...

  8. Stages of Esophageal Cancer

    Science.gov (United States)

    ... the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds , ... stage of the cancer being treated. External and internal radiation therapy are used to treat esophageal cancer. A plastic ...

  9. Stages of Anal Cancer

    Science.gov (United States)

    ... the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds , ... stage of the cancer being treated. External and internal radiation therapy are used to treat anal cancer. Chemotherapy Chemotherapy ...

  10. Stages of Penile Cancer

    Science.gov (United States)

    ... the body to send radiation toward the cancer. Internal radiation therapy uses a radioactive substance sealed in needles, seeds , ... stage of the cancer being treated. External and internal radiation therapy are used to treat penile cancer. Chemotherapy Chemotherapy ...

  11. Staging interrail mobilities

    DEFF Research Database (Denmark)

    Jensen, Martin Trandberg; Gyimóthy, Szilvia; Jensen, Ole B.

    2016-01-01

    This article applies the multiscalar ‘staging mobilities’ framework from the emergent subfield of mobilities design to analyse an enduring European rail travel phenomenon, interrail. This discussion extends and contributes to tourism mobilities research. Second, the article enriches previous...

  12. Environmental magnetic fields: Influences on early embryogenesis

    Energy Technology Data Exchange (ETDEWEB)

    Cameron, I.L.; Hardman, W.E.; Winters, W.D.; Zimmerman, S.; Zimmerman, A.M. (Univ. of Texas Health Science Center, San Antonio (United States))

    1993-04-01

    A 10-mG, 50 to 60-Hz magnetic field is in the intensity and frequency range that people worldwide are often exposed to in homes and in the workplace. Studies about the effects of 50- to 100-Hz electromagnetic fields on various species of animal embryos (fish, chick, fly, sea urchin, rat, and mouse) indicate that early stages of embryonic development are responsive to fluctuating magnetic fields. Chick, sea urchin, and mouse embryos are responsive to magnetic field intensities of 10-100 mG. Results from studies on sea urchin embryos indicate that exposure to conditions of rotating 60-Hz magnetic fields, e.g., similar to those in our environment, interferes with cell proliferation at the morula stage in a manner dependent on field intensity. The cleavage stages, prior to the 64-cell stage, were not delayed by this rotating 60-Hz magnetic field suggesting that the ionic surges, DNA replication, and translational events essential for early cleavage stages were not significantly altered. Studies of histone synthesis in early sea urchin embryos indicated that the rotating 60-Hz magnetic field decreased zygotic expression of early histone genes at the morula stage and suggests that this decrease in early histone production was limiting to cell proliferation. Whether these comparative observations from animal development studies will be paralleled by results from studies of human embryogenesis, as suggested by some epidemiology studies, has yet to be established. 38 refs.

  13. Stages of ores formation

    International Nuclear Information System (INIS)

    Khasanov, A.Kh.

    1988-01-01

    Deposit formation (especially endogenous) is the complicated, multi-stage and long process. Establishment of deposit formation succession, age-specific correlations of minerals and aggregates have a high importance at solving genetic questions. Studying of minerals correlations and mineral aggregates, succession of their crystallization and other observations let restore the history of deposit formation, pick up in it different on duration and physical and chemical conditions stages

  14. Magnet Systems

    Data.gov (United States)

    Federal Laboratory Consortium — Over the decades, Fermilab has been responsible for the design, construction, test and analysis of hundreds of conventional and superconducting accelerator magnets...

  15. Planetary Magnetism

    International Nuclear Information System (INIS)

    Russell, C.T.

    1980-01-01

    Planetary spacecraft have now probed the magnetic fields of all the terrestrial planets, the moon, Jupiter, and Saturn. These measurements reveal that dynamos are active in at least four of the planets, Mercury, the earth, Jupiter, and Saturn but that Venus and Mars appear to have at most only very weak planetary magnetic fields. The moon may have once possessed an internal dynamo, for the surface rocks are magnetized. The large satellites of the outer solar system are candidates for dynamo action in addition to the large planets themselves. Of these satellites the one most likely to generate its own internal magnetic field is Io

  16. Magnetics Processing

    Data.gov (United States)

    Federal Laboratory Consortium — The Magnetics Processing Lab equipped to perform testing of magnetometers, integrate them into aircraft systems, and perform data analysis, including noise reduction...

  17. Magnetic resonance imaging of the prostate

    DEFF Research Database (Denmark)

    Iversen, P; Kjaer, L; Thomsen, C

    1988-01-01

    Magnetic resonance imaging offers new possibilities in investigation of the prostate gland. Current results of imaging and tissue discrimination in the evaluation of prostatic disease are reviewed. Magnetic resonance imaging may be useful in the staging of carcinoma of the prostate....

  18. Magnetic resonance imaging of the prostate

    DEFF Research Database (Denmark)

    Iversen, P; Kjaer, L; Thomsen, C

    1987-01-01

    Magnetic resonance imaging offers new possibilities in the investigation of the prostate. The current results of imaging and tissue discrimination in the evaluation of prostatic disease are reviewed. Magnetic resonance imaging may be of value in the staging of carcinoma of the prostate....

  19. DC-based magnetic field controller

    Science.gov (United States)

    Kotter, Dale K.; Rankin, Richard A.; Morgan, John P,.

    1994-01-01

    A magnetic field controller for laboratory devices and in particular to dc operated magnetic field controllers for mass spectrometers, comprising a dc power supply in combination with improvements to a hall probe subsystem, display subsystem, preamplifier, field control subsystem, and an output stage.

  20. A Bright Future for Magnetic Resonance

    Indian Academy of Sciences (India)

    IAS Admin

    Does magnetic resonance have a bright future? Ever since magnetic resonance in condensed phase started in 1945, questions about its future prospects (or its imminent doom) have been asked time and again. Some, like Nicolaas Bloembergen, left the field at an early stage because they felt there was no hope to gather ...

  1. Superconducting magnet systems in EPR designs

    International Nuclear Information System (INIS)

    Knobloch, A.F.

    1976-10-01

    Tokamak experiments have reached a stage where large scale application of superconductors can be envisaged for machines becoming operational within the next decade. Existing designs for future devices already indicate some of the tasks and problems associated with large superconducting magnet systems. Using this information the coming magnet system requirements are summarized, some design considerations given and in conclusion a brief survey describes already existing Tokamak magnet development programs. (orig.) [de

  2. Dynamics of a Chain of Permanent Magnets

    OpenAIRE

    Lee , Joosung; Boisson , Jean; Rouby , Corinne; Doaré , Olivier; Ducceschi , Michele; Bodelot , Laurence

    2015-01-01

    International audience; An arrangement of several spherical or cylindrical magnets presents different stable configurations. One of them is the straight chain, whose dynamics is studied in the present work. This structure behaves similarly to a beam, but here the rigidity is exclusively due to magnetic forces. Theoretically, the dynamical equations of the structure are obtained by first providing an expression of the energies involved in the system. At this stage, the magnetic interactions ar...

  3. Chemotherapy Toxicity On Quality of Life in Older Patients With Stage I, Stage II, Stage III, or Stage IV Ovarian Epithelial, Primary Peritoneal Cavity, or Fallopian Tube Cancer

    Science.gov (United States)

    2017-05-03

    Stage I Ovarian Cancer; Stage IA Fallopian Tube Cancer; Stage IB Fallopian Tube Cancer; Stage IC Fallopian Tube Cancer; Stage II Ovarian Cancer; Stage IIA Fallopian Tube Cancer; Stage IIB Fallopian Tube Cancer; Stage IIC Fallopian Tube Cancer; Stage III Ovarian Cancer; Stage III Primary Peritoneal Cancer; Stage IIIA Fallopian Tube Cancer; Stage IIIB Fallopian Tube Cancer; Stage IIIC Fallopian Tube Cancer; Stage IV Fallopian Tube Cancer; Stage IV Ovarian Cancer; Stage IV Primary Peritoneal Cancer

  4. Staging in Patients with Small-Cell Lung Carcinoma; PET-CT versus Standard Staging Procedures

    Directory of Open Access Journals (Sweden)

    Burcu Yalçın

    2016-12-01

    Full Text Available Objective: The most important factor for accurate treatment of patients with small cell lung carcinoma (SCLC is accuracy of the initial staging. The aim of this study was to determine how often patients, staged as local or local-advanced disease by standard staging procedures (SSPs, would be staged to have a metastatic disease based on the findings of the positron emission tomography–computed tomography (PET-CT scan. Methods: Patients with SCLC who were staged as I, II, or III disease by SSPs (according to the American Joint Committee on Cancer Staging, 7th edition formed the study population. SSPs included computed tomography of chest, abdomen, brain (or magnetic resonance imaging of brain, and bone scintigraphy. These patients were re-staged with 18F-FDG PET-CT scan. Results: Between 2013 and 2015, 27 patients were prospectively studied. Of these patients, 92.5% were male and the median age was 61. Among 27 patients, distant metastasis was detected by PET-CT in 7 (25.9% patients. Two of 7 patients were determined as stage IIIA by SSPs and 5 of 17 patients that were determined as stage IIIB by SSPs were upstaged to metastatic disease by PET-CT. All of the 7 patients had bone metastasis by PET-CT. But bone metastasis could not be detected with bone scintigraphy. Conclusion: PET-CT detected distant metastasis in one quarter of SCLC stage III patients by SSPs. Patients who staged local-advanced SCLC with CT of the chest have to be assessed by PET-CT for extracranial distant metastasis.

  5. Magnetic Resonance Imaging (MRI) -- Head

    Medline Plus

    Full Text Available ... at a very early stage by mapping the motion of water molecules in the tissue. This water motion, known as diffusion, is impaired by most strokes, ... that magnetic resonance imaging harms the fetus, pregnant women usually are advised not to have an MRI ...

  6. Greenhouse effect in quiescent prominences

    Science.gov (United States)

    Ryutova, M.; Berger, T. E.; Title, A. M.

    2010-12-01

    Quiescent prominences, by definition, are huge ``clouds'' of cool, dense plasma overlying rarefied hot corona and supported by a complex magnetic field anchored in the photosphere along the magnetic polarity inversion line. One of the most prominent features in their dynamics is formation, growth and collapse of bubble/cavities filled by coronal plasma and emerging, often repeatedly, under a prominence body. As such, prominence/corona interface itself is subject of fundamental plasma instabilities, which include development of a regular series of plumes and spikes typical to the Rayleigh-Taylor instability, the Kelvin-Helmholtz instability, often followed by a sudden collimated mass upflow, which, in nonlinear stage having an explosive character may be responsible for CMEs. These were only recently studied in detail with high cadence, high resolution data obtained from the Hinode satellite. Even more surprises are brought by the SDO/AIA instrument showing the Sun's atmosphere in 12 visible and EUV wavelengths. AIA multi-wavelength images in a temperature range from 105 ~K to 2 × 106 ~K combined with the Hinode/SOT data show that plasma inside the prominence cavity, being as expected, at coronal temperatures, in fact exceeds the temperature of the ambient corona. We suggest that an energetically open highly dynamic processes releasing energy at the prominence/cavity interface accompanied by the ``radiative exchange'', may cause additional increase of temperature and/or density inside cavity. Given pervasive character of prominences, future studies will allow us to perform quantitative and statistical analysis, and reveal relations between the size of cavity, its temperature, and magnetic properties.

  7. Experimental study of the Richtmyer-Meshkov instability induced by a Mach 3 shock wave

    International Nuclear Information System (INIS)

    BP Puranik; JG Oakley; MH Anderson; R Bonaazza

    2003-01-01

    OAK-B135 An experimental investigation of a shock-induced interfacial instability (Richtmyer-Meshkov instability) is undertaken in an effort to study temporal evolution of interfacial perturbations in the late stages of development. The experiments are performed in a vertical shock tube with a square cross-section. A membraneless interface is prepared by retracting a sinusoidally shaped metal plate initially separating carbon dioxide from air, with both gases initially at atmospheric pressure. With carbon dioxide above the plate, the Rayleigh-Taylor instability commences as the plate is retracted and the amplitude of the initial sinusoidal perturbation imposed on the interface begins to grow. The interface is accelerated by a strong shock wave (M=3.08) while its shape is still sinusoidal and before the Kelvin-Helmhotz instability distorts it into the well known mushroom-like structures; its initial amplitude to wavelength ratio is large enough that the interface evolution enters its nonlinear stage very shortly after shock acceleration. The pre-shock evolution of the interface due to the Rayleigh-Taylor instability and the post-shock evolution of the interface due to the Richtmyer-Meshkov instability are visualized using planar Mie scattering. The pre-shock evolution of the interface is carried out in an independent set of experiments. The initial conditions for the Richtmyer-Meshkov experiment are determined from the pre-shock Rayleigh-Taylor growth. One image of the post-shock interface is obtained per experiment and image sequences, showing the post-shock evolution of the interface, are constructed from several experiments. The growth rate of the perturbation amplitude is measured and compared with two recent analytical models of the Richtmyer-Meshkov instability

  8. A comparative study of ultrasonography, computed tomography and magnetic resonance imaging in the staging and invasion of adjacent structures by renal tumors; Estudo comparativo dos metodos de ultrassonografia, tomografia computadorizada e ressonancia magnetica no estadiamento e invasao das estruturas adjacentes por tumores renais

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, S.M.; Ajzen, S.A.; Trindade, J.C.S. [Universidade Federal de Sao Paulo (UNIFESP), SP (Brazil). Faculdade de Medicina; UNESP, Botucatu, SP (Brazil). Faculdade de Medicina; E-mail: sribeiro@fmb.unesp.br

    2001-09-01

    Ultrasonography (US), Computed Tomography (CT), and Magnetic Resonance imaging (MR) were compared for the staging of renal tumors. The differences between these imaging techniques were also studied for their ability to detect adenopathies, vascular invasion, distant intra-abdominal metastases, and particularly adjacent organ invasion. Thirty-one patients with solid or complex renal masses were prospectively studied using US, CT, and MR. Differences between the results obtained were studied using the Cochran G test and the Mc NEMAR test. The sensitivity and specificity of each diagnostic technique were compared against a 'gold standard' of the surgical and histopathological findings. The following sensitivities were obtained: For the detection of adenopathy, US 63.6%, CT and MR 90.9%. For vascular invasion, US 42.8%, CT and MR 85.7%. For the adjacent organ invasion, US 28.5%, CT 85.7%, and MR 71.4%. Some of the criteria that suggest invasion of adjacent structures include: the envelopment of the adjacent structures by the tumor, tumor extension into the adjacent structures with an irregular appearance, and alterations in shape, size, and density of adjacent structures. Loss of fat planes between the tumor and adjacent structures is not a sign of tumor invasion. Significant differences were found in the detection capacity of US in relation to CT and MR, which were similar. All three techniques were highly sensitive and specific only in the detection of distant abdominal metastases. In addition to the accuracy of these diagnostic modalities for the detection and staging of tumors, invasiveness, risks and cost should be considered in relation to relative costs and benefits. (author)

  9. Magnetic Field

    DEFF Research Database (Denmark)

    Olsen, Nils

    2015-01-01

    of the fluid flow at the top of the core. However, what is measured at or near the surface of the Earth is the superposition of the core field and fields caused by magnetized rocks in the Earth’s crust, by electric currents flowing in the ionosphere, magnetosphere, and oceans, and by currents induced......he Earth has a large and complicated magnetic field, the major part of which is produced by a self-sustaining dynamo operating in the fluid outer core. Magnetic field observations provide one of the few tools for remote sensing the Earth’s deep interior, especially regarding the dynamics...... in the Earth by time-varying external fields. These sources have their specific characteristics in terms of spatial and temporal variations, and their proper separation, based on magnetic measurements, is a major challenge. Such a separation is a prerequisite for remote sensing by means of magnetic field...

  10. Single conversion stage amplifier - SICAM

    Energy Technology Data Exchange (ETDEWEB)

    Ljusev, P.

    2005-12-15

    This Ph.D. thesis presents a thorough analysis of the so called SICAM - SIngle Converter stage AMplifier approach to building direct energy conversion audio power amplifiers. The mainstream approach for building isolated audio power amplifiers today consists of isolated DC power supply and Class D amplifier, which essentially represents a two stage solution, where each of the components can be viewed as separate and independent part. The proposed SICAM solution strives for direct energy conversion from the mains to the audio output, by dedicating the operation of the components one to another and integrating their functions, so that the final audio power amplifier represents a single-stage topology with higher efficiency, lower volume, less board space, lower component count and subsequently lower cost. The SICAM approach is both applicable to non-isolated and isolated audio power amplifiers, but the problems encountered in these two cases are different. Non-isolated SICAM solutions are intended for both AC mains-connected and battery-powered devices. In non-isolated mains-connected SICAMs the main idea is to simplify the power supply or even provide integrated power factor correction (PFC) functions, while still maintaining low component stress and good audio performance by generally decreasing the input voltage level to the Class D audio power amplifier. On the other hand, non-isolated battery-powered SICAMs have to cope with the ever changing battery voltage and provide output voltage levels which are both lower and higher than the battery voltage, while still being simple and single-stage energy conversion solutions. In isolated SICAMs the isolation transformer adjusts the voltage level on the secondary side to the desired level, so the main challenges here are decreasing the size of the magnetic core and reducing the number and size of bulky reactive components as much as possible. The main focus of this thesis is directed towards the isolated SICAMs and

  11. Composers on stage

    DEFF Research Database (Denmark)

    Groth, Sanne Krogh

    A trend on the scene of contemporary music is composers going on stage, performing their pieces themselves. Within a discourse of popular music, this is more the rule than exception, but when it comes to the context of contemporary scored music, the historical and aesthetic context differs......, and something quite different is undergoing. This paper intends to discuss three examples of performances in which the composer’s appearance on stage was an important part of the piece, - both when it came to the role as a performer and as an individual person – as representer and presenter. The paper intends...... to rise the following questions: What happens to the status of the author, when he suddenly (re-)appears on stage? How is this appearance to be understood in both a contemporary and historical context: Is it the musical virtuous appearing again, are we witnessing musical works turning...

  12. Magnetic refrigerator for hydrogen liquefaction

    Energy Technology Data Exchange (ETDEWEB)

    Numazawa, T [National Institute for Materials Science, Tsukuba (Japan); Kamlya, K. [Japan Atomic Energy Agency, Naka (Japan); Utaki, T. [Osaka University, Osaka (Japan); Matsumoto, K. [Kanazawa University, Kanazawa (Japan)

    2013-06-15

    This paper reviews the development status of magnetic refrigeration system for hydrogen liquefaction. There is no doubt that hydrogen is one of most important energy sources in the near future. In particular, liquid hydrogen can be utilized for infrastructure construction consisting of storage and transportation. Liquid hydrogen is in cryogenic temperatures and therefore high efficient liquefaction method must be studied. Magnetic refrigeration which uses the magneto-caloric effect has potential to realize not only the higher liquefaction efficiency > 50 %, but also to be environmentally friendly and cost effective. Our hydrogen magnetic refrigeration system consists of Carnot cycle for liquefaction stage and AMR (active magnetic regenerator) cycle for precooling stages. For the Carnot cycle, we develop the high efficient system > 80 % liquefaction efficiency by using the heat pipe. For the AMR cycle, we studied two kinds of displacer systems, which transferred the working fluid. We confirmed the AMR effect with the cooling temperature span of 12 K for 1.8 T of the magnetic field and 6 second of the cycle. By using the simulation, we estimate the total efficiency of the hydrogen liquefaction plant for 10 kg/day. A FOM of 0.47 is obtained in the magnetic refrigeration system operation temperature between 20 K and 77 K including LN2 work input.

  13. Magnetic susceptibility and magnetic resonance measurements of the moisture content and hydration condition of a magnetic mixture material

    International Nuclear Information System (INIS)

    Tsukada, K.; Kusaka, T.; Saari, M. M.; Takagi, R.; Sakai, K.; Kiwa, T.; Bito, Y.

    2014-01-01

    We developed a magnetic measurement method to measure the moisture content and hydration condition of mortar as a magnetic mixture material. Mortar is a mixture of Portland cement, sand, and water, and these materials exhibit different magnetic properties. The magnetization–magnetic field curves of these components and of mortars with different moisture contents were measured, using a specially developed high-temperature-superconductor superconducting quantum interference device. Using the differences in magnetic characteristics, the moisture content of mortar was measured at the ferromagnetic saturation region over 250 mT. A correlation between magnetic susceptibility and moisture content was successfully established. After Portland cement and water are mixed, hydration begins. At the early stage of the hydration/gel, magnetization strength increased over time. To investigate the magnetization change, we measured the distribution between bound and free water in the mortar in the early stage by magnetic resonance imaging (MRI). The MRI results suggest that the amount of free water in mortar correlates with the change in magnetic susceptibility

  14. Magnetic susceptibility and magnetic resonance measurements of the moisture content and hydration condition of a magnetic mixture material

    Energy Technology Data Exchange (ETDEWEB)

    Tsukada, K., E-mail: tsukada@cc.okayama-u.ac.jp; Kusaka, T.; Saari, M. M.; Takagi, R.; Sakai, K.; Kiwa, T. [The Graduate School of Natural Science and Technology, Okayama University, 3-1-1 Tsushima-Naka, Okayama 700-8530 (Japan); Bito, Y. [Central Research Lab., Hitachi. Ltd., 1-280 Higashi-Koigakubo, Kokubunji, Tokyo 185-8601 (Japan)

    2014-05-07

    We developed a magnetic measurement method to measure the moisture content and hydration condition of mortar as a magnetic mixture material. Mortar is a mixture of Portland cement, sand, and water, and these materials exhibit different magnetic properties. The magnetization–magnetic field curves of these components and of mortars with different moisture contents were measured, using a specially developed high-temperature-superconductor superconducting quantum interference device. Using the differences in magnetic characteristics, the moisture content of mortar was measured at the ferromagnetic saturation region over 250 mT. A correlation between magnetic susceptibility and moisture content was successfully established. After Portland cement and water are mixed, hydration begins. At the early stage of the hydration/gel, magnetization strength increased over time. To investigate the magnetization change, we measured the distribution between bound and free water in the mortar in the early stage by magnetic resonance imaging (MRI). The MRI results suggest that the amount of free water in mortar correlates with the change in magnetic susceptibility.

  15. Staging Collaborative Innovation Processes

    DEFF Research Database (Denmark)

    Pedersen, Signe; Clausen, Christian

    Organisations are currently challenged by demands for increased collaborative innovation internally as well as with external and new entities - e.g. across the value chain. The authors seek to develop new approaches to managing collaborative innovative processes in the context of open innovation...... and public private innovation partnerships. Based on a case study of a collaborative design process in a large electronics company the paper points to the key importance of staging and navigation of collaborative innovation process. Staging and navigation is presented as a combined activity: 1) to translate...

  16. Cognitive phenotypes of sequential staging in amyotrophic lateral sclerosis.

    Science.gov (United States)

    Lulé, Dorothée; Böhm, Sarah; Müller, Hans-Peter; Aho-Özhan, Helena; Keller, Jürgen; Gorges, Martin; Loose, Markus; Weishaupt, Jochen H; Uttner, Ingo; Pinkhardt, Elmar; Kassubek, Jan; Del Tredici, Kelly; Braak, Heiko; Abrahams, Sharon; Ludolph, Albert C

    2018-04-01

    Sequential spread of TDP-43 load in the brain may be a pathological characteristic of amyotrophic lateral sclerosis (ALS). Diffusion tensor imaging (DTI) is a magnetic resonance imaging (MRI) based marker of this pathological feature. Cognitive deficits known to be present in a subset of ALS patients might act as an additional in vivo clinical marker of disease spread. N = 139 patients with ALS were tested with the Edinburgh Cognitive and Behavioural ALS screen (ECAS) in addition to DTI brain measures of pathological spread. Executive function, memory and disinhibited behaviour were selected for Cognitive-Staging criteria, as these cognitive functions are attributed to cerebral areas analogous to the pattern of MRI markers of TDP-43 pathology. ROC curve analyses were performed to define cut-off scores for cognitive stages 2 (executive function), stage 3 (disinhibited behaviour) and stage 4 (memory), and staging was performed according to the cognitive profile subsequently. Associations of Cognitive-Staging (stage 2-4) and MRI-Staging measures were determined. In total, 77 patients (55%) performed below ROC cut-off scores in either executive function or memory or both and/or were reported to have disinhibited behaviour which permitted Cognitive-Staging. The cognitive profile of patients with discrete MRI stages 2-4 correlated significantly with DTI parameters. For those patients with cognitive impairment, there was a high congruency between MRI and Cognitive-Staging with high specificity and sensitivity of executive functions for MRI stage 2, disinhibited behaviour for MRI stage 3 and moderate of memory for MRI stage 4. Cognitive impairment follows specific patterns in ALS and these patterns can be used for Cognitive-Staging with a high specificity compared to MRI-Staging. For the individual, cognitive screening is a fast and easy to apply measurement of cerebral function giving valuable information in a clinical context. Copyright © 2018 Elsevier Ltd. All

  17. Whole-body magnetic resonance imaging for staging and follow-up of pediatric patients with Hodgkin's lymphoma: comparison of different sequences; Aplicacao da ressonancia magnetica de corpo inteiro para o estadiamento e acompanhamento de pacientes com linfoma de Hodgkin na faixa etaria infanto-juvenil: comparacao entre diferentes sequencias

    Energy Technology Data Exchange (ETDEWEB)

    Nava, Daniel; Oliveira, Heverton Cesar de, E-mail: daniel@centrus.com.b [Universidade Federal de Sao Paulo (UNIFESP/EPM), SP (Brazil). Dept. de Diagnostico por Imagem; Luisi, Flavio Augusto; Lederman, Henrique Manoel [Universidade Federal de Sao Paulo (UNIFESP/IOP/GRAACC), SP (Brazil). Inst. de Oncologia Pediatrica. Grupo de Apoio ao Adolescente e a Crianca com Cancer; Ximenes, Andrea Regina da Silveira [Clinica Centrus, Campinas, SP (Brazil)

    2011-07-01

    Objective: to compare the performance of the T1, T2, STIR and DWIBS (diffusion-weighted whole-body imaging with background body signal suppression) sequences in the staging and follow-up of pediatric patients with Hodgkin's lymphoma in lymph node chains, parenchymal organs and bone marrow, and to evaluate interobserver agreement. Materials and methods: the authors studied 12 patients with confirmed diagnosis of Hodgkin's lymphoma. The patients were referred for whole body magnetic resonance imaging with T1-weighted, T2-weighted, STIR and DWIBS sequences. Results: the number of lymph node sites characterized as affected by the disease on T1- and T2-weighted sequences showed similar results (8 sites for both sequences), but lower than DWIBS and STIR sequences (11 and 12 sites, respectively). The bone marrow involvement by lymphoma showed the same values for the T1-, T2-weighted and DWIBS sequences (17 lesions), higher than the value found on STIR (13 lesions). A high rate of interobserver agreement was observed as the four sequences were analyzed. Conclusion: STIR and DWIBS sequences detected the highest number of lymph node sites characterized as affected by the disease. Similar results were demonstrated by all the sequences in the evaluation of parenchymal organs and bone marrow. A high interobserver agreement was observed as the four sequences were analyzed. (author)

  18. End-stage kidney disease

    Science.gov (United States)

    ... medlineplus.gov/ency/article/000500.htm End-stage kidney disease To use the sharing features on this page, please enable JavaScript. End-stage kidney disease (ESKD) is the last stage of long-term ( ...

  19. Magnetic field measurements of Fermilab/General Dynamics built full scale SSC collider dipole magnets

    International Nuclear Information System (INIS)

    Delchamps, S.; Bleadon, M.; Bossert, R.; Carson, J.; Gourlay, S.; Hanft, R.; Koska, W.; Kuchnir, M.; Lamm, M.J.; Mazur, P.O.; Mokhtarani, A.; Orris, D.; Strait, J.; Wake, M.; Devred, A.; DiMarco, J.; Kuzminski, J.; Ogitsu, T.; Puglisi, M.; Tompkins, J.C.; Yu, Y.; Zhao, Y.; Zheng, H.

    1992-01-01

    This paper presents preliminary results of magnetic field measurements made on a series of 50 mm aperture 15 m long SSC collider dipole magnets designed and manufactured at Fermi National Accelerator Laboratory (Fermilab) for use in the Superconducting Super Collider Laboratory (SSCL) Accelerator System String Test. The magnets were assembled by Fermilab and General Dynamics personnel, and were tested at the Magnet Test Facility (MTF) at Fermilab. Measurements of the dipole field angle, dipole field strength, and field shape parameters at various stages in magnet construction and testing are described

  20. "Stage 40" Handbook.

    Science.gov (United States)

    Mill River Union High School, North Clarendon, VT.

    The policies, purposes, and guidelines of "Stage 40," an educational repertory company for students, are presented in this paper, which also explains how the company functions. The paper discusses the company's history, the relationship between the company and academics, and the responsibilities of a company member. Letters by the board…