Neutrons, Surfaces, and Skin

Fig. 12. a Neutron reflectivity data for a 860 A-thick PMDA-3F/PPO triblock film which has been foamed for 4 h. The line through the data is the fit using the scattering density profile shown in b. b Scattering length density profiles for a unfoamed and foamed PMDA-3F/PPO triblock. The foaming results in a decrease in the overall film thickness and an increase in the density of the skin layer, particularly at the air interface. The density in the center of the film corresponds to about 15% voids, density skin at the top and bottom surfaces of the film... 

For P-particles, aluminum foil will stop their penetration. Thus, a protective suit will prevent P-particles from reaching the skin, where they can burn and cause surface contamination. a-Particles can enter the lungs and cause the tissue to become electrically charged (ionized). Protection from a-particles can be obtained with the use of air-purifying respirators with proper cartridges to filter out radioactive particles. Neutrons are found around the core of a nuclear reactor and are absorbed by both water and the material in the control rods of the reactor. If a worker is not close to the core of the reactor, then no exposure can occur. 

The supersolid skin contains molecules upto two layers. A comparative study using x-ray and neutron scattering, sum-frequency vibrational spectroscopy and calorimetric measurements of the interaction between water and hydrophobic surface, as well as molecular-statistical calculations of the state of water molecules in the skin prove that the boundary water layer in the vicinity of hydrophobic surface consists of a thin ( 0.5 nm) depletion layer. The density is as low as 0.4 g/cm (correspond to doo = 3.66 A) and a considerable amount (25-30 %) of water molecules with free OH groups, which is characterized by a more ordered network of H-bonds compared to liquid water [22, 23]. 

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