Light-particle emission versus evaporation residue formation in collisions of40Ar onnatCa at 30 MeV/u

The closely associated phenomena of preequilibrium emission and evaporation residue formation in fusion-like reactions were studied in central collisions between⁴⁰Ar and^natCa at 30 MeV/u. Heavy reaction products were taken in coincidence with neutrons and light charged particles. The preequilibrium neutron data agree very well with predictions of a quantal phase-space model which, in addition to the mean field, takes two-body collisions properly into account. Preequilibrium emission ends in thermally equilibrated hot nuclei with an average excitation energy of about 6 MeV/u. The combined results show a striking interrelation between the missing mass and light-particle multiplicities: the mass difference between the full compound mass and the observed residues can be explained quantitatively by the emission of only neutrons and light charged particles withZ2 during the entire course of energy dissipation.Supported by the German Bundesministerium für Forschung und Technologie (BMFT) under contract 06 HD 983I     

How Fast can a Subharmonic Function Decay Along a Ray?

Much is known about the connection between the growth and decayof subharmonic functions. The results indicate that there isa general principle: asubharmonic function cannot decay ‘toofast’ relative to its growth.Three theorems are provedwhich, together with work previously published elsewhere, givea fairly complete account of how this principle works out fora subharmonic function having extremal decay along a ray. 1991Mathematics Subject Classification: 30D20, 31A05.     

Percolation and fragmentation of excited atomic nuclei

We present an analysis which aims at explaining the similarities (and differences) which exist between a simple bond percolation process on a cubic lattice and the fragmentation of highly excited atomic nuclei. Emphasis is placed on discussing percolation in terms of concepts which are well known in nuclear physics such asQ-value and particle emission thresholds. Similarities and differences between the bond percolation process and nuclear fragmentation are discussed. An approximate expression for the microcanonical partition sum (number of microstates) corresponding to any given percolation partition is shown to provide a good starting point for predicting fragment size distributions.Communicated by: X. Campi     

Comparison of human skull and spherical shell vibrations—implications for head injury modeling

Spherical shell models have been formulated as geometric approximations of the human head. By insuring geometrical and material similarity between the model and human head, impact response and skull fracture studies were expected to yield results in close agreement with model predictions. This, however, was not the case. Model predictions of skull fracture loads were typically twice the observed level. A comparison was made between the resonant frequencies of two dry human skulls and corresponding spherical shell models. Poor agreement was observed. A vibrational analysis of the model revealed that the uniformity of the spherical shell approximmately doubles the effective stiffness and resonant frequencies as compared with the dry human skull. The elastic modulus of the model was adjusted to bring its resonances into closer agreement with those of the skull. The synthesized“effective” modulus was 50% lower than the material property of human cranial bone. Interestingly, this adjustment also brought model predictions of skull fracture into closer agreement with available human cadaver data.     

Quantitation of melphalan in plasma of patients by reversed-phase high-performance liquid chromatography with electrochemical detection

An analytical procedure for the separation and determination of melphalan in human plasma was carried out. A simple high-performance liquid chromatographic method with electrochemical detection was developed taking advantage of the high sensitivity of the electrode redox reaction. The sample pretreatment consisted of a direct extraction of the interferents rather than of melphalan, owing to the difficulty of extraction of the drug, and was very simple, rapid and reproducible.