Biomedical subjects

A Shaulov

Publications and source records attributed to A Shaulov.

11 recordsLinked to original sources

PubMed2006

Flux-flow resistivity anisotropy in the instability regime of the a-b plane of epitaxial superconducting YBa2Cu3O7-delta thin films.

Measurements of the nonlinear flux-flow resistivity rho and the critical vortex velocity vphi* at high voltage bias close to the instability regime predicted by Larkin and Ovchinnikov (Z. Eksp. Teor. Fiz 68, 1915 (1975) [Sov. Phys. JETP 41, 960 (1976)]) are reported along the node and antinode directions of the d-wave order parameter in the a-b plane of epitaxial YBa2Cu3O7-delta films. In this pinning-free regime, rho and vphi* are found to be anisotropic with values in the node direction larger on average by 10% than in the antinode direction. The anisotropy of rho is almost independent of temperature and field. We attribute the observed results to the anisotropic quasiparticle distribution on the Fermi surface of YBa2Cu3O7-delta.

Journal Article↗

PubMed2001

A major fraction of human bone marrow lymphocytes are Th2-like CD1d-reactive T cells that can suppress mixed lymphocyte responses.

Murine bone marrow (BM) NK T cells can suppress graft-vs-host disease, transplant rejection, and MLRs. Human BM contains T cells with similar potential. Human BM was enriched for NK T cells, approximately 50% of which recognized the nonpolymorphic CD1d molecule. In contrast to the well-characterized blood-derived CD1d-reactive invariant NK T cells, the majority of human BM CD1d-reactive T cells used diverse TCR. Healthy donor invariant NK T cells rapidly produce large amounts of IL-4 and IFN-gamma and can influence Th1/Th2 decision-making. Healthy donor BM CD1d-reactive T cells were Th2-biased and suppressed MLR and, unlike the former, responded preferentially to CD1d(+) lymphoid cells. These results identify a novel population of human T cells which may contribute to B cell development and/or maintain Th2 bias against autoimmune T cell responses against new B cell Ag receptors. Distinct CD1d-reactive T cell populations have the potential to suppress graft-vs-host disease and stimulate antitumor responses.

Antigens, CD1↗

PubMed2001

Loss of IFN-gamma production by invariant NK T cells in advanced cancer.

Invariant NK T cells express certain NK cell receptors and an invariant TCRalpha chain specific for the MHC class I-like CD1d protein. These invariant NK T cells can regulate diverse immune responses in mice, including antitumor responses, through mechanisms including rapid production of IL-4 and IFN-gamma, but their physiological functions remain uncertain. Invariant NK T cells were markedly decreased in peripheral blood from advanced prostate cancer patients, and their ex vivo expansion with a CD1d-presented lipid Ag (alpha-galactosylceramide) was diminished compared with healthy donors. Invariant NK T cells from healthy donors produced high levels of both IFN-gamma and IL-4. In contrast, whereas invariant NK T cells from prostate cancer patients also produced IL-4, they had diminished IFN-gamma production and a striking decrease in their IFN-gamma:IL-4 ratio. The IFN-gamma deficit was specific to the invariant NK T cells, as bulk T cells from prostate cancer patients produced normal levels of IFN-gamma and IL-4. These findings support an immunoregulatory function for invariant NK T cells in humans mediated by differential production of Th1 vs Th2 cytokines. They further indicate that antitumor responses may be suppressed by the marked Th2 bias of invariant NK T cells in advanced cancer patients.

Cells, Cultured↗

PubMed2000

Transient vortex states in Bi2Sr2CaCu2O(8+delta) crystals

A high temporal resolution magneto-optical system is employed to observe the time evolution of the vortex structure in Bi(2)Sr(2)CaCu(2)O(8+delta) crystals after a sudden application of a magnetic field. The magneto-optical images reveal dynamic coexistence of two vortex phases: a quasiordered phase in the sample interior and a transient disordered phase near the sample edges. The border between these two phases, marked by an abrupt change in the gradient of the local induction, moves with time. This motion enables tracing the decay of the transient state and the concurrent growth of the thermodynamic vortex phases. The growth rate is sensitive to the location in the field-temperature phase diagram.

Journal Article↗

PubMed1996