Lambda spectra in 11.6A GeV/c Au-Au collisions.

E896 has measured Lambda production in 11.6A GeV/c Au-Au collisions over virtually the whole rapidity phase space. The midrapidity p(t) distributions have been measured for the first time at this energy and appear to indicate that the Lambda hyperons have different freeze-out conditions than protons. A comparison with the relativistic quantum molecular dynamics model shows that while there is good shape agreement at high rapidity the model predicts significantly different slopes of the m(t) spectra at midrapidity. The data, where overlap occurs, are consistent with previously reported measurements.

Synergistic effects of vasopressin plus epinephrine during cardiopulmonary resuscitation.

Both epinephrine (Epi) and vasopressin (VP) increase coronary perfusion pressure (CPP) when administered during cardiac arrest. Given their different mechanisms of action we tested the hypothesis that during cardiopulmonary resuscitation (CPR) a combination of VP plus Epi would be superior to either agent alone. Epi(40 microg/kg), VP(0.3 U/kg) and the combination of both agents were assessed in a porcine model of ventricular fibrillation (VF). Maximum CPP (diastolic aortic-right atrial pressures) during CPR was similar among the groups but the time course of action was different in each group: with Epi + VP the increase in CPP was significantly more rapid than with VP alone whereas the CPP remained significantly higher for a longer periods of time with VP or VP + Epi versus Epi alone. Left ventricular blood flow (ml/min per g) determined during CPR two min after drug administration was similar between groups: Epi 1.06 +/- 0.16; VP 0.82 +/- 0.26; Epi + VP 0.83 +/- 0.14 (P = N.S.). Post drug administration. 2 min, cerebral blood flow (ml/min per g) in the VP group (0.76 +/- 0.15) was more than two times higher compared with Epi alone (Epi:0.30 +/- 0.08, P < 0.01 versus VP) and Epi plus VP (Epi + VP:0.23 +/- 0.03, P < 0.01 versus VP). We conclude that combination of VP + Epi during cardiac arrest results in a more rapid rise in CPP when compared with VP alone and a more sustained elevation in CPP than observed with Epi alone. Thus, the synergistic effects of these two potent vasopressor agents may be of benefit during CPR.

A program to measure new energetic particle nuclear interaction cross sections.

The Transport Collaboration, consisting of researchers from institutions in France, Germany, Italy and the USA, has established a program to make new measurements of nuclear interaction cross sections for heavy projectiles (Z > or = 2) in targets of liquid H2, He and heavier materials. Such cross sections directly affect calculations of galactic and solar cosmic ray transport through matter and are needed for accurate radiation hazard assessment. To date, the collaboration has obtained data using the LBL Bevalac HISS facility with 20 projectiles from 4He to 58Ni in the energy range 393-910 MeV/nucleon. Preliminary results from the analysis of these data are presented here and compared to other measurements and to cross section prediction formulae.

Fragmentation of nitrogen-14 nuclei at 2.1 gev per nucleon.

An experiment has been carried out at the bevatron on the nuclear fragmentation of nitrogen-14 ions at an energy of 2.1 billion electron volts (Gev) per nucleon. Because of the near equality of the velocities of the nitrogen-14 beam and the fragmentation products at an angle of 0 degrees , we find it possible to identify the nuclear fragments isotopically.

Auroral-particle precipitation and trapping caused by electrostatic double layers in the ionosphere.

Interpretation of high-resolution angular distribution measurements of the primary auroral electron flux detected by a rocket probe launched into a visible aurora from Fort Churchill in the fall of 1966 leads to the following conclusions. The auroral electron flux is nearly monoenergetic and has a quasi-trapped as well as a precipitating component. The quasi-trapped flux appears to be limited to a region defined by magnetic-mirror points and multiple electrostatic double layers in the ionosphere. The electrostatic field of the double-layer distribution enhances the aurora by lowering the magnetic-mirror points and supplying energy to the primary auroral electrons.