Bulgeless dwarf galaxies and dark matter cores from supernova-driven outflows.

For almost two decades the properties of 'dwarf' galaxies have challenged the cold dark matter (CDM) model of galaxy formation. Most observed dwarf galaxies consist of a rotating stellar disk embedded in a massive dark-matter halo with a near-constant-density core. Models based on the dominance of CDM, however, invariably form galaxies with dense spheroidal stellar bulges and steep central dark-matter profiles, because low-angular-momentum baryons and dark matter sink to the centres of galaxies through accretion and repeated mergers. Processes that decrease the central density of CDM halos have been identified, but have not yet reconciled theory with observations of present-day dwarfs. This failure is potentially catastrophic for the CDM model, possibly requiring a different dark-matter particle candidate. Here we report hydrodynamical simulations (in a framework assuming the presence of CDM and a cosmological constant) in which the inhomogeneous interstellar medium is resolved. Strong outflows from supernovae remove low-angular-momentum gas, which inhibits the formation of bulges and decreases the dark-matter density to less than half of what it would otherwise be within the central kiloparsec. The analogues of dwarf galaxies-bulgeless and with shallow central dark-matter profiles-arise naturally in these simulations.

Hapten inhibition of dextran anaphylaxis. Nine years of post-marketing surveillance of dextran 1.

All spontaneous reports to the manufacturer and to WHO's database INTDIS regarding adverse reactions to clinical dextran after preinjection of dextran 1 and to dextran 1 alone 1983-1991 were collected. During 1983-1991 a total of 4.8 million doses of Promit were sold in fourteen countries. The incidence of severe DIAR (grades III-V) to clinical dextran after the prophylactic use of hapten inhibition was approximately one case per 200,000 doses of dextran 1. In Sweden, where reporting of severe adverse drug reactions is mandatory, the incidence was one case per 70,000. This indicates a 35-fold reduction in the incidence of severe DIAR compared with the use of clinical dextran without dextran 1. Only two fatal reactions were reported; the incidence was therefore one case per 2.4 million doses, indicating a 77-fold reduction. Both these occurred in patients with extremely high titers of DRA. Side effects to dextran 1, mostly mild, were reported in one case per 100,000 doses. These side effects were not antibody mediated. It is concluded that the introduction of hapten inhibition with dextran 1 has greatly reduced the risk for serious side effects to dextran, making dextran one of the safest colloids in use.

KrF laser-pumped dye-laser studies.

Dye-laser efficiency measurements were performed on four Coumarin dyes: C-485, C-498, C-500, and C-503, all operating near 500 nm. They were pumped with a 16-ns pulse-length KrF laser. The most efficient of the Coumarin dyes tested was C-498. The intrinsic efficiency of this dye was found to increase with pump rate. At a pump rate of 2 MW/cm(2), an intrinsic efficiency of > 20% was measured. Longer KrF laser pulses (> 1.2 µs) were also used to pump C-498 and resulted in comparable laser efficiencies at similar pump rates. The temporal relationship between the input KrF laser pump pulse and the output dye-laser pulse was studied and was found to differ significantly for long and short pulses. Significant improvement in long-pulse laser performance was observed when the laser-cavity configuration incorporated a skip mode.