Search Results - (Author, Cooperation:M. Chance)

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  1. 1
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    Publication Date:
    2015-06-13
    Publisher:
    American Association for the Advancement of Science (AAAS)
    Print ISSN:
    0036-8075
    Electronic ISSN:
    1095-9203
    Topics:
    Biology
    Chemistry and Pharmacology
    Computer Science
    Medicine
    Natural Sciences in General
    Physics
    Keywords:
    Animals ; Bone Marrow Transplantation ; Colitis/enzymology/prevention & control ; Dinoprostone/metabolism ; Enzyme Inhibitors/chemistry/pharmacology ; Hematopoiesis/drug effects ; Hydroxyprostaglandin Dehydrogenases/antagonists & inhibitors/genetics/*physiology ; Liver Regeneration/drug effects ; Mice ; Mice, Knockout ; Prostaglandins/*metabolism ; Pyridines/chemistry/pharmacology ; Regeneration/drug effects/genetics/*physiology ; Thiophenes/chemistry/pharmacology
    Published by:
    http://www.aaas.org/

    Latest Papers from Table of Contents or Articles in Press
  2. 2
    Chance, M. S.

    [S.l.] : American Institute of Physics (AIP)
    Published 1997
    Staff View
    ISSN:
    1089-7674
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A robustly accurate and effective method is presented to solve Laplace's equation in general azimuthally symmetric geometry for the magnetic scalar potential in the region surrounding a plasma discharge which may or may not contain external conductors. These conductors can be topologically toroidal or spherical, and may have toroidal gaps in them. The solution is incorporated into the various magnetohydrodynamic stability codes either through the volume integrated perturbed magnetic energy in the vacuum region or through the continuity requirements for the normal component of the perturbed magnetic field and the total perturbed pressure across the unperturbed plasma–vacuum boundary. The method is based upon using Green's second identity and the method of collocation. As useful by-products, the eddy currents and the simulation of Mirnov loop measurements are calculated.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.872380

    Articles: DFG German National Licenses
  3. 3
    D'Ippolito, D. A. ; Myra, J. R. ; Jardin, S. C. ; Chance, M. S. ; Valeo, E. J.

    [S.l.] : American Institute of Physics (AIP)
    Published 1995
    Staff View
    ISSN:
    1089-7674
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A novel mechanism for feedback stabilization of external kink modes and disruptions is proposed in which modulated radio-frequency (RF) antennas apply a stabilizing ponderomotive force (PF) to the plasma. The RF power required for n=1 kink stabilization in the Princeton Beta Experiment-Modified (PBX-M) [Phys. Fluids B 2, 1271 (1990)] is estimated, and it is shown that the idea can be tested with the existing antenna system. A simulation of a preliminary n=0 modulation experiment on PBX-M also shows that the PF can balance applied vertical field oscillations. © 1995 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.871448

    Articles: DFG German National Licenses
  4. 4
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    ISSN:
    1089-7674
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A proof of principle magnetic feedback stabilization experiment has been carried out to suppress the resistive wall mode (RWM), a branch of the ideal magnetohydrodynamic (MHD) kink mode under the influence of a stabilizing resistive wall, on the DIII-D tokamak device [Plasma Phys. Controlled Fusion Research (International Atomic Energy Agency, Vienna, 1986), p. 159; Phys. Plasmas 1, 1415 (1994)]. The RWM was successfully suppressed and the high beta duration above the no-wall limit was extended to more than 50 times the resistive wall flux diffusion time. It was observed that the mode structure was well preserved during the time of the feedback application. Several lumped parameter formulations were used to study the feedback process. The observed feedback characteristics are in good qualitative agreement with the analysis. These results provide encouragement to future efforts towards optimizing the RWM feedback methodology in parallel to what has been successfully developed for the n=0 vertical positional control. Newly developed MHD codes have been extremely useful in guiding the experiments and in providing possible paths for the next step. © 2001 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.1351823

    Articles: DFG German National Licenses
  5. 5
    Staff View
    ISSN:
    1089-7674
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The amplitude and frequency of modes driven in the edge region of tokamak high mode (H-mode) discharges [type I edge-localized modes (ELMs)] are shown to depend on the discharge shape. The measured pressure gradient threshold for instability and its scaling with discharge shape are compared with predictions from ideal magnetohydrodynamic theory for low toroidal mode number (n) instabilities driven by pressure gradient and current density and good agreement is found. Reductions in mode amplitude are observed in discharge shapes with either high squareness or low triangularity where the stability threshold in the edge pressure gradient is predicted to be reduced and the most unstable mode is expected to have higher values of n. The importance of access to the ballooning mode second stability regime is demonstrated through the changes in the ELM character that occur when second regime access is not available. An edge stability model is presented that predicts that there is a threshold value of n for second regime access and that the most unstable mode has n near this threshold. © 2000 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.874053

    Articles: DFG German National Licenses
  6. 6
    Rewoldt, G. ; Beer, M. A. ; Chance, M. S. ; Hahm, T. S. ; Lin, Z. ; Tang, W. M.

    [S.l.] : American Institute of Physics (AIP)
    Published 1998
    Staff View
    ISSN:
    1089-7674
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Sheared rotation dynamics are widely believed to have significant influence on experimentally-observed confinement transitions in advanced operating modes in major tokamak experiments, such as the Tokamak Fusion Test Reactor (TFTR) [D. J. Grove and D. M. Meade, Nucl. Fusion 25, 1167 (1985)], with reversed magnetic shear regions in the plasma interior. The high-n toroidal drift modes destabilized by the combined effects of ion temperature gradients and trapped particles in toroidal geometry can be strongly affected by radially-sheared toroidal and poloidal plasma rotation. In previous work with the FULL linear microinstability code, a simplified rotation model including only toroidal rotation was employed, and results were obtained. Here, a more complete rotation model, which includes contributions from toroidal and poloidal rotation and the ion pressure gradient to the total radial electric field, is used for a proper self-consistent treatment of this key problem. Relevant advanced operating mode cases for TFTR are presented. In addition, the complementary problem of the dynamics of fluctuation-driven E×B flow is investigated by an integrated program of gyrokinetic simulation in annulus geometry and gyrofluid simulation in flux tube geometry. © 1998 American Institute of Physics.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.872851

    Articles: DFG German National Licenses
  7. 7
    Manickam, J. ; Chance, M. S. ; Jardin, S. C. ; Kessel, C. ; Monticello, D. ; Pomphrey, N. ; Reiman, A. ; Wang, C. ; Zakharov, L. E.

    [S.l.] : American Institute of Physics (AIP)
    Published 1994
    Staff View
    ISSN:
    1089-7674
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Stability analysis of advanced regime tokamaks is presented. Here advanced regimes are defined to include configurations where the ratio of the bootstrap current, IBS, to the total plasma current, Ip, approaches unity, and the normalized stored energy, βN* = 80π〈p2〉1/2a/IpB0, has a value greater than 4.5. Here, p is the plasma pressure, a the minor radius in meters, Ip is in mega-amps, B0 is the magnetic field in Tesla, and 〈⋅〉 represents a volume average. Specific scenarios are discussed in the context of Toroidal Physics Experiment (TPX) [Proceedings of the 20th European Physical Society Conference on Controlled Fusion and Plasma Physics, Lisbon, 1993, edited by J. A. Costa Cabral, M. E. Manso, F. M. Serra, and F. C. Schuller (European Physical Society, Petit-Lancy, 1993), p. I-80]. The best scenario is one with reversed shear, in the q profile, in the central region of the tokamak. The bootstrap current obtained from the plasma profiles provides 90% of the required current, and is well aligned with the optimal current profile for ideal magnetohydrodynamic stability. This configuration is stable up to βN*≈ 6.8, if the external boundary conditions are relaxed to those corresponding to an ideal structure at a moderate distance of approximately 1.3 times the minor radius.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.870660

    Articles: DFG German National Licenses
  8. 8
    Park, W. ; Parker, S. ; Biglari, H. ; Chance, M. ; Chen, L. ; Cheng, C. Z. ; Hahm, T. S. ; Lee, W. W. ; Kulsrud, R. ; Monticello, D. ; Sugiyama, L. ; White, R.

    New York, NY : American Institute of Physics (AIP)
    Published 1992
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A three-dimensional (3-D) hybrid gyrokinetic-MHD (magnetohydrodynamic) simulation scheme is presented. To the 3-D toroidal MHD code, MH3D-K the energetic particle component is added as gyrokinetic particles. The resulting code, mh3d-k, is used to study the nonlinear behavior of energetic particle effects in tokamaks, such as the energetic particle stabilization of sawteeth, fishbone oscillations, and alpha-particle-driven toroidal Alfvén eigenmode (TAE) modes.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.860011

    Articles: DFG German National Licenses
  9. 9
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Recent operation of the Tokamak Fusion Test Reactor (TFTR) [Plasma Phys. Controlled Nucl. Fusion Research 1, 51 (1986)] has produced plasma equilibria with values of Λ≡βp eq+li/2 as large as 7, εβp dia≡2μ0ε〈p⊥〉/〈〈Bp〉〉2 as large as 1.6, and Troyon normalized diamagnetic beta [Plasma Phys. Controlled Fusion 26, 209 (1984); Phys. Lett. 110A, 29 (1985)], βNdia≡108〈βt⊥〉aB0/Ip as large as 4.7. When εβp dia(approximately-greater-than)1.25, a separatrix entered the vacuum chamber, producing a naturally diverted discharge that was sustained for many energy confinement times, τE. The largest values of εβp and plasma stored energy were obtained when the plasma current was ramped down prior to neutral beam injection. The measured peak ion and electron temperatures were as large as 24 and 8.5 keV, respectively. Plasma stored energy in excess of 2.5 MJ and τE greater than 130 msec were obtained. Confinement times of greater than 3 times that expected from L-mode predictions have been achieved. The fusion power gain QDD reached a value of 1.3×10−3 in a discharge with Ip=1 MA and εβp dia=0.85. A large, sustained negative loop voltage during the steady-state portion of the discharge indicates that a substantial noninductive component of Ip exists in these plasmas. Transport code analysis indicates that the bootstrap current constitutes up to 65% of Ip. Magnetohydrodynamic (MHD) ballooning stability analysis shows that, while these plasmas are near, or at the βp limit, the pressure gradient in the plasma core is in the first region of stability to high-n modes.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.859647

    Articles: DFG German National Licenses
  10. 10
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The highly indented plasmas of the PBX-M tokamak experiment [Plasma Physics and Controlled Nuclear Fusion Research (IAEA, Vienna, 1989), Vol. 1, p. 97] have reached plasma regimes of both high volume-averaged beta (βt), and high-beta poloidal (βp), and show evidence of the suppression of external surface modes by the passive stabilizing system. Values of βt up to 4.0 I/aB (% MA/m T) with Ti(0)≈4 keV have been obtained. A magnetohydrodynamic analysis of plasmas with βp=2.0 indicates that these plasmas are near the threshold of the second stability regime. A value of βt of 6.8% has been reached with Ti(0)〉5 keV and an indentation of 28%. Control of plasma shape is accomplished with a feedback system that uses a moment expansion about a single equilibrium and is augmented by time-dependent waveforms to redefine plasma shape. Diagnostics to measure the safety factor q have been developed and used to make accurate measurements of q(r) and to verify changes made in q(0).
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.859542

    Articles: DFG German National Licenses
  11. 11
    Chu, M. S. ; Chance, M. S. ; Greene, J. M. ; Jensen, T. H.

    New York, NY : American Institute of Physics (AIP)
    Published 1989
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A self-adjoint, gauge invariant stability functional δWTG for determination of a sufficient condition of tearing mode stability is obtained for a plasma with a uniform pressure. The plasma is stable if there is no free energy available to support energy flux into the singular layer. The Δ' concept, valid in simple geometries, is generalized to reflect variation of equilibrium quantities on the flux surface. The relationship of δWTG to the ideal stability functional and other possible forms of tearing mode stability functionals is clarified through gauge transformations.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.859105

    Articles: DFG German National Licenses
  12. 12
    Turnbull, A. D. ; Chu, M. S. ; Chance, M. S. ; Greene, J. M. ; Lao, L. L. ; Strait, E. J.

    New York, NY : American Institute of Physics (AIP)
    Published 1992
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A variational ideal magnetohydrodynamic stability code is used to compute the toroidicity-induced Alfvén eigenmode (TAE) for toroidal mode number n=1 in full toroidal geometry with circular cross section. At finite aspect ratio, toroidicity also couples poloidal mode numbers m with m+2 to produce a higher frequency gap in the shear Alfvén spectrum, which is associated with a new, second-order TAE mode. It is also found that toroidal coupling between the TAE modes and continuum branches induces splitting of the TAE modes into two or more global modes at slightly different frequencies. Both the new modes and splitting of the TAE modes have important consequences for the identification of TAE modes in experiments.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.860352

    Articles: DFG German National Licenses
  13. 13
    Chu, M. S. ; Chance, M. S. ; Greene, J. M. ; Jensen, T. H.

    New York, NY : American Institute of Physics (AIP)
    Published 1990
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    A self-adjoint, gauge invariant stability functional δWTG for determination of a sufficient condition of tearing mode stability is obtained for a plasma with arbitrary current and pressure profiles. The plasma is stable if there is no free energy available to support energy flux into the singular layer. The pressure gradient near the singular layer is found to be stabilizing. The tearing mode energy drive is extracted by casting the problem into its nonlinear context, demanding that both large and small solutions be continuous across the singular layer.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.859492

    Articles: DFG German National Licenses
  14. 14
    Dagazian, R. Y. ; Chance, M. S.

    [S.l.] : American Institute of Physics (AIP)
    Published 1985
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    Various toroidal reversed-field pinch (RFP) equilibria stable to ideal Mercier and ballooning modes are subjected to resistive ballooning analysis. The stability properties of these configurations are thus investigated as a function of quantities that are experimentally measurable. Resistive ballooning is seen as a likely candidate for the interpretation of a certain class of density fluctuation phenomena observed in these devices.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.865041

    Articles: DFG German National Licenses
  15. 15
    Cheng, C. Z. ; Chance, M. S.

    [S.l.] : American Institute of Physics (AIP)
    Published 1986
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    In toroidal plasmas, the toroidal magnetic field is nonuniform over a magnetic surface and causes coupling of different poloidal harmonics. It is shown both analytically and numerically that the toroidicity not only breaks up the shear Alfvén continuous spectrum, but also creates new, discrete, toroidicity-induced shear Alfvén eigenmodes with frequencies inside the continuum gaps. Potential applications of the low-n toroidicity-induced shear Alfvén eigenmodes on plasma heating and instabilities are addressed.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.865801

    Articles: DFG German National Licenses
  16. 16
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The experimental program of the Princeton Beta Experiment-Modified (PBX-M) tokamak [Phys. Fluids B2, 1271 (1990)] is directed toward tailoring plasma profiles to achieve greater stability and confinement and to gain access to the second stability region. Modification of the current density profile has been achieved with lower-hybrid current drive (LHCD), leading to a regime free of global magnetohydrodynamic modes, while raising the value of q(0) above unity. The diffusion of the fast electrons produced by LHCD has been examined using two-dimensional hard x-ray imaging. Ion Bernstein waves (IBW) have been used for ion heating: a preliminary analysis shows that ion heating was spatially localized and in agreement with theoretical calculations. Divertor biasing has modified the electric field inside the last closed surface, resulting in the formation of a transport barrier, which in turn has reduced the threshold power of neutral beam injection (NBI) for H-mode transition by 25%.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.860744

    Articles: DFG German National Licenses
  17. 17
    Chu, M. S. ; Greene, J. M. ; Lao, L. L. ; Turnbull, A. D. ; Chance, M. S.

    New York, NY : American Institute of Physics (AIP)
    Published 1992
    Staff View
    ISSN:
    1089-7666
    Source:
    AIP Digital Archive
    Topics:
    Physics
    Notes:
    The toroidicity-induced gaps of the shear Alfvén wave spectrum in tokamaks are shown to satisfy an envelope equation. The structure of these gaps, and the location of the high-n gap modes, which are localized modes with frequency in the gap, are studied for general numerically generated equilibria. The dependence of the frequencies of the gaps and the gap modes on the equilibrium properties, such as elongation, triangularity, and β of the plasma are explored.
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1063/1.860327

    Articles: DFG German National Licenses
  18. 18
    BENESCH, R. ; CHANCE, M. R. A. ; GLYNN, L. E.

    [s.l.] : Nature Publishing Group
    Published 1945
    Staff View
    ISSN:
    1476-4687
    Source:
    Nature Archives 1869 - 2009
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Notes:
    [Auszug] THE recent demonstration by Golding and Silver1 that certain sulphonamides act as inhibitors of phosphatase in vitro has led us to present a preliminary report of our investigations on the effect of sulphonamides on bone formation in vivo. These experiments were designed to ...
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1038/155203a0

    Articles: DFG German National Licenses
  19. 19
    NEW, R. R. C. ; CHANCE, M. L. ; THOMAS, S. C. ; PETERS, W.

    [s.l.] : Nature Publishing Group
    Published 1978
    Staff View
    ISSN:
    1476-4687
    Source:
    Nature Archives 1869 - 2009
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Notes:
    [Auszug] Liposomes were prepared from lecithin (purified from egg yolk by the method of Pangborn3) by ultrasonication as described by Bangham and Home4. Lecithin (200 mg) was dispersed in 10 ml fluid, and sonicated in the cold for 5 min. For liposomes containing drug, 2 g either of antimony potassium ...
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1038/272055a0

    Articles: DFG German National Licenses
  20. 20
    CHANCE, M. R. A.

    [s.l.] : Nature Publishing Group
    Published 1956
    Staff View
    ISSN:
    1476-4687
    Source:
    Nature Archives 1869 - 2009
    Topics:
    Biology
    Chemistry and Pharmacology
    Medicine
    Natural Sciences in General
    Physics
    Notes:
    [Auszug] Studies of the influence of factors in the environment of the immature female rat receiving serum gonadotrophin have revealed that they take a major part in determining not only the sensitivity of the ovarian-weight response, but more especially the variability within the group. The following is a ...
    Type of Medium:
    Electronic Resource
    URL:
    http://dx.doi.org/10.1038/177228a0

    Articles: DFG German National Licenses