Dilepton production and mTm_T-scaling at BEVALAC/SIS energies

We present a dynamical study of $e^+e^-$ production in C + C and Ca + Ca collisions at BEVALAC/SIS energies on the basis of the covariant transport approach HSD employing momentum-dependent $\rho$-meson spectral functions that include the pion modifications in the nuclear medium as well as the polarization of the $\rho$-meson due to resonant $\rho - N$ scattering. We find that the experimental data from the DLS collaboration cannot be described within the $\rho$-meson spectral function approach. A dropping $\eta$-mass scenario leads to a good reproduction of the DLS dilepton data, however, violates the $m_T$-scaling of $\pi^0$ and $\eta$ spectra as observed by the TAPS collaboration as well as $\eta$ photoproduction on nuclei.Comment: 35 pages, ReVTeX, including 11 postscript figures, UGI-97-06, Nucl. Phys. A, in pres

Photoinactivation of T-Cell Function with Psoralen and UVA Radiation Suppresses the Induction of Experimental Murine Graft-Versus-Host Disease Across Major Histocompatibility Barriers

Bone marrow transplantation is employed in the treatment of a number of hematologic and malignant diseases. A major complication is the induction of graft-versus-host disease. Whereas removal of T lymphocytes from the donor marrow effectively reduces the incidence of graft-versus-host disease, the incidence of graft failure often increases when T cells are depleted from the transplanted marrow. In the current study, photoinactivation of the donor cells with 8-methoxypsoralen coupled with exposure to long-wavelength ultraviolet radiation (PUVA therapy) was used to inactivate the response of the donor T cells against the host. PUVA therapy suppressed the ability of spleen cells to respond to alloantigen in the in vitro mixed lymphocyte reaction. The induction of acute graft-versus-host disease across complete major histocompatibility barriers in lethally X-irradiated mice was significantly suppressed after bone marrow transplantation with photoinactivated bone marrow cells. Long-term survivors demonstrated allogeneic reconstitution and partial restoration of T-cell function. Because PUVA therapy had no inhibitory effect on hematopoiesis, these data suggest that using phototherapy to inactivate the alloreactivity of T cells may provide an alternative to purging T cells from the donor marrow, thus suppressing both the incidence of graft-versus-host disease and the incidence of graft failure