3D molecular imaging SIMS

Thin monolayer and bilayer films of spin cast poly(methyl methacrylate) (PMMA), poly(2-hydroxyethyl methacrylate) (PHEMA), poly(lactic) acid (PLA) and PLA doped with several pharmaceuticals have been analyzed by dynamic SIMS using SF₅⁺ polyatomic primary ion bombardment. Each of these systems exhibited minimal primary beam-induced degradation under cluster ion bombardment allowing molecular depth profiles to be obtained through the film. By combing secondary ion imaging with depth profiling, three-dimensional molecular image depth profiles have been obtained from these systems. In another approach, bevel cross-sections are cut in the samples with the SF₅⁺ primary ion beam to produce a laterally magnified cross-section of the sample that does not contain the beam-induced damage that would be induced by conventional focussed ion beam (FIB) cross-sectioning. The bevel surface can then be examined using cluster SIMS imaging or other appropriate microanalysis technique.     

Studies of the protein and the energy metabolism in man during a wintering in Antarctica

During the 29th Soviet Antarctic Expedition in Novolazarevskaya from March 1984 to March 1985, the protein and energy metabolisms were studied in six expeditioners from the German Democratic Republic. The investigations were carried out at the beginning of the expedition (May), during the polar night (July) and during the polar day (December). The effect of a special stress situation (sledge trek in April 1984) was investigated in one subject. The stable nitrogen isotope (15)N was used to study the protein metabolism. The assessment of the energy metabolism was based on the oxygen consumption, which was determined by means of a spirograph. In addition, the vital capacity, the breath minute volume, the blood pressure, etc. were measured. The following results were obtained: During the polar night, the utilisation of the dietary proteins and the whole body protein synthesis calculated by means of the (15)N excretion of the total nitrogen in urine were greater (73.6±0.9 % and 3.48±0.17?g protein d(-1)?kg(-1), n=3) than the respective values during the polar day (69.7±1.2, p<0.05, n=3 and 3.05±0.07, p<0.05, n=3) and at the beginning of the expedition (69.6±1.4, p<0.02, n=5 and 2.81±0.09, p<0.01, n=5). The lowest values (58.0 % and 2.43?g protein d(-1)?kg(-1)) were obtained in the subject after the trek. The resting metabolic rate (in kJ?d(-1)?m(-2)) was decreased during the polar night (45.6±5.0, n=4) in comparison with the polar day (61.5±11.3, n=3) and the beginning of the expedition (52.3±9.6, n=4) with p<0.01 in both cases.     

Excitation-energy sharing in uranium induced dissipative collisions

Strongly damped collisions were studied in uranium induced reactions on¹¹⁰Pd and¹²⁴Sn target nuclei near the barrier. The excitation-energy splitting was deduced from binary reaction yields and those in which the heavy fragment undergoes sequential fission. For systems with 87≦Z≦95 for the heavy fragment, the excitation energy is concentrated in the lighter nucleus, at best shared equally. The results indicate a non-equilibrated energy dissipation, and support nucleon exchange based on average single-particle strength functions as the underlying dissipation mechanism at the barrier.