The Experts below are selected from a list of 276 Experts worldwide ranked by ideXlab platform

Hermann Rauh - One of the best experts on this subject based on the ideXlab platform.

V. V. Derevyanko - One of the best experts on this subject based on the ideXlab platform.

  • Magnetoresistance of granular YBa 2 Cu 3 O 7 - δ HTSC in weak magnetic field: Angular dependence
    Physics of the Solid State, 2007
    Co-Authors: V. V. Derevyanko, T. V. Sukhareva, V. A. Finkel
    Abstract:

    The magnetoresistance of ceramic YBa2Cu3O∼6.5 HTSC samples is studied as a function of the mutual orientation of the current I and external magnetic field Hext at T = 77.3 K in magnetic fields of up to ∼500 Oe. It is found that, if the demagnetization factor D is taken into account, the effective critical field of Complete Penetration of Josephson vortices into weak links Hc2Jeff does not depend on the mutual orientation of I and Hext. The lower critical field Hc1Aeff associated with the beginning of Penetration of Abrikosov vortices into superconducting grains increases substantially with the angle between I and Hext. The strongest variation with the mutual orientation of I and Hext is exhibited by the critical field of the Bragg glass-vortex glass first-order phase transition HBG-VGeff and by the magnetoresistance jump at this phase transition.

  • Penetration of a magnetic field into the YBa2Cu3O7−δ high-temperature superconductor: Magnetoresistance in weak magnetic fields
    Physics of the Solid State, 2004
    Co-Authors: V. V. Derevyanko, T. V. Sukhareva, V. A. Finkel
    Abstract:

    The Penetration of a magnetic field into superconducting grains and weak links of YBa2Cu3O7−δ ceramic high-temperature superconductors is investigated using measurements of the transverse and longitudinal magnetoresistances at T=77.3 K and 0≤H≤∼500 Oe as a function of the transport current in the range ∼0.01≤I/Ic≤∼0.99. The effects associated with the Complete Penetration of Josephson vortices into weak links of the high-temperature superconductor in magnetic fields Hc2J, the onset of Penetration of Abrikosov vortices into superconducting grains in magnetic fields Hc1A, and the first-order transition from the Bragg glass phase to the vortex glass phase in fields HBG-VG are revealed and interpreted. The I-H phase diagrams YBa2Cu3O7−δ high-temperature superconductors are constructed for I ⊥ H and I ‖ H.

  • Penetration of a magnetic field into the YBa_2Cu_3O_7−δ high-temperature superconductor: Magnetoresistance in weak magnetic fields
    Physics of the Solid State, 2004
    Co-Authors: V. V. Derevyanko, T. V. Sukhareva, V. A. Finkel’
    Abstract:

    The Penetration of a magnetic field into superconducting grains and weak links of YBa_2Cu_3O_7−δ ceramic high-temperature superconductors is investigated using measurements of the transverse and longitudinal magnetoresistances at T =77.3 K and 0≤ H ≤∼500 Oe as a function of the transport current in the range ∼0.01≤ I / I _ c ≤∼0.99. The effects associated with the Complete Penetration of Josephson vortices into weak links of the high-temperature superconductor in magnetic fields H _ c 2 J , the onset of Penetration of Abrikosov vortices into superconducting grains in magnetic fields H _ c 1 A , and the first-order transition from the Bragg glass phase to the vortex glass phase in fields H _BG-VG are revealed and interpreted. The I-H phase diagrams YBa_2Cu_3O_7−δ high-temperature superconductors are constructed for I ⊥ H and I ‖ H .

V. A. Finkel - One of the best experts on this subject based on the ideXlab platform.

  • Magnetoresistance of granular YBa 2 Cu 3 O 7 - δ HTSC in weak magnetic field: Angular dependence
    Physics of the Solid State, 2007
    Co-Authors: V. V. Derevyanko, T. V. Sukhareva, V. A. Finkel
    Abstract:

    The magnetoresistance of ceramic YBa2Cu3O∼6.5 HTSC samples is studied as a function of the mutual orientation of the current I and external magnetic field Hext at T = 77.3 K in magnetic fields of up to ∼500 Oe. It is found that, if the demagnetization factor D is taken into account, the effective critical field of Complete Penetration of Josephson vortices into weak links Hc2Jeff does not depend on the mutual orientation of I and Hext. The lower critical field Hc1Aeff associated with the beginning of Penetration of Abrikosov vortices into superconducting grains increases substantially with the angle between I and Hext. The strongest variation with the mutual orientation of I and Hext is exhibited by the critical field of the Bragg glass-vortex glass first-order phase transition HBG-VGeff and by the magnetoresistance jump at this phase transition.

  • Penetration of a magnetic field into the YBa2Cu3O7−δ high-temperature superconductor: Magnetoresistance in weak magnetic fields
    Physics of the Solid State, 2004
    Co-Authors: V. V. Derevyanko, T. V. Sukhareva, V. A. Finkel
    Abstract:

    The Penetration of a magnetic field into superconducting grains and weak links of YBa2Cu3O7−δ ceramic high-temperature superconductors is investigated using measurements of the transverse and longitudinal magnetoresistances at T=77.3 K and 0≤H≤∼500 Oe as a function of the transport current in the range ∼0.01≤I/Ic≤∼0.99. The effects associated with the Complete Penetration of Josephson vortices into weak links of the high-temperature superconductor in magnetic fields Hc2J, the onset of Penetration of Abrikosov vortices into superconducting grains in magnetic fields Hc1A, and the first-order transition from the Bragg glass phase to the vortex glass phase in fields HBG-VG are revealed and interpreted. The I-H phase diagrams YBa2Cu3O7−δ high-temperature superconductors are constructed for I ⊥ H and I ‖ H.

Christian A Voigt - One of the best experts on this subject based on the ideXlab platform.

  • interaction of the arabidopsis gtpase raba4c with its effector pmr4 results in Complete Penetration resistance to powdery mildew
    The Plant Cell, 2014
    Co-Authors: Dorothea Ellinger, Annemarie Glockner, Jasmin Koch, Marcel Naumann, Vanessa Sturtz, Kevin Schutt, Chithra Manisseri, Shauna C Somerville, Christian A Voigt
    Abstract:

    The (1,3)-β-glucan callose is a major component of cell wall thickenings in response to pathogen attack in plants. GTPases have been suggested to regulate pathogen-induced callose biosynthesis. To elucidate the regulation of callose biosynthesis in Arabidopsis thaliana, we screened microarray data and identified transcriptional upregulation of the GTPase RabA4c after biotic stress. We studied the function of RabA4c in its native and dominant negative (dn) isoform in RabA4c overexpression lines. RabA4c overexpression caused Complete Penetration resistance to the virulent powdery mildew Golovinomyces cichoracearum due to enhanced callose deposition at early time points of infection, which prevented fungal ingress into epidermal cells. By contrast, RabA4c(dn) overexpression did not increase callose deposition or Penetration resistance. A cross of the resistant line with the pmr4 disruption mutant lacking the stress-induced callose synthase PMR4 revealed that enhanced callose deposition and Penetration resistance were PMR4-dependent. In live-cell imaging, tagged RabA4c was shown to localize at the plasma membrane prior to infection, which was broken in the pmr4 disruption mutant background, with callose deposits at the site of attempted fungal Penetration. Together with our interactions studies including yeast two-hybrid, pull-down, and in planta fluorescence resonance energy transfer assays, we concluded that RabA4c directly interacts with PMR4, which can be seen as an effector of this GTPase.

  • elevated early callose deposition results in Complete Penetration resistance to powdery mildew in arabidopsis
    Plant Physiology, 2013
    Co-Authors: Dorothea Ellinger, Marcel Naumann, Chithra Manisseri, Shauna C Somerville, Christian Falter, Claudia Zwikowics, Torsten Jamrow, Christian A Voigt
    Abstract:

    A common response by plants to fungal attack is deposition of callose, a (1,3)-β-glucan polymer, in the form of cell wall thickenings called papillae, at site of wall Penetration. While it has been generally believed that the papillae provide a structural barrier to slow fungal Penetration, this idea has been challenged in recent studies of Arabidopsis (Arabidopsis thaliana), where fungal resistance was found to be independent of callose deposition. To the contrary, we show that callose can strongly support Penetration resistance when deposited in elevated amounts at early time points of infection. We generated transgenic Arabidopsis lines that express POWDERY MILDEW RESISTANT4 (PMR4), which encodes a stress-induced callose synthase, under the control of the constitutive 35S promoter. In these lines, we detected callose synthase activity that was four times higher than that in wild-type plants 6 h post inoculation with the virulent powdery mildew Golovinomyces cichoracearum. The callose synthase activity was correlated with enlarged callose deposits and the focal accumulation of green fluorescent protein-tagged PMR4 at sites of attempted fungal Penetration. We observed similar results from infection studies with the nonadapted powdery mildew Blumeria graminis f. sp. hordei. Haustoria formation was prevented in resistant transgenic lines during both types of powdery mildew infection, and neither the salicylic acid-dependent nor jasmonate-dependent pathways were induced. We present a schematic model that highlights the differences in callose deposition between the resistant transgenic lines and the susceptible wild-type plants during compatible and incompatible interactions between Arabidopsis and powdery mildew.

Sergey V. Yampolskii - One of the best experts on this subject based on the ideXlab platform.