Microstructure of bulk polymers as revealed in ultrathin sections

An improved method is described for obtaining ultrathin sections of soft polymers for examination in the electron microscope. The method involves cooling the specimens in the temperature range 0 to ?160°C. during sectioning. The method has proved particularly useful for the study of microstructure in bulk polymers, especially semi-crystalline materials such as polyethylene. The visibility of some features can be improved by electron staining. Preliminary results obtained on polyethylene and polypropylene are illustrated and discussed.     

The determination of wear elements in lubricating oils by neutron activation analysis

Used lubricating oil analysis programs are currently employed by both the military and industry in an attempt to minimize some of the costs associated with equipment failure. The periodic determination of water elements in the lubricant of an oil-wetted system can provide very useful information on the condition or health of the system and an early indication of impending failure. In the present study, the application of Neutron Activation Analysis (NAA) to used oil analysis was investigated. The method developed allowed for the determination of fifteen elements (Ag, Al, Cl, Cr, Cu, Fe, In, Mg, Mn, Mo, Na, Ni, Sn, Ti and Zn) associated with engine wear or deterioration. Results obtained for the analysis of used naval diesel oils exhibited good agreement with results obtained by Atomic Absorption Spectrophotometry (AAS) methods. A drawback of the NAA procedure is that the determination of Fe, a major wear element in most systems, involves an analysis time of approximately one week.     

Twisting Behaviour of Conformal Maps

This paper is devoted to the study of different types of twistingpoints of conformal maps. We define the sets of gyration, spiraland oscillation points and we prove, in the case that f is conformalalmost nowhere, that the above sets have Hausdorff dimensionone. Also we define points of bounded radial oscillation. Itis proved that there are always points of -bounded radial oscillationbut there exists a conformal map without points of small boundedradial oscillation.     

Comparison of the transmission behavior of a triazeno-polymer with a theoretical model

The threshold fluence,F _Th, of ablation of a triazeno-polymer was measured in the low fluence range for thin films using conventional UV-spectroscopy. It was found that there is a clearly definedF _Th for 308 nm irradiation between 20 and 25 mJ cm^–2. In the case of 248 nm irradiation, a threshold fluence range between 16 and 32 MJ cm^–2 was found. The ablation rate for both irradiation wavelengths depends on film-thickness. For the XeCl excimer-laser, the point at which the rate becomes independent of thickness was observed to lie at a value which did not correspond to the calculated laser penetration depth, whereas for the KrF laser the independence was not reached within the applied thickness range (up to 0.35 m). Additional transmission measurements have been performed showing that the target transmission at 248 nm increases only slightly, whereas for 308 nm the transmission increases by a factor of approximately 4. This result shows that dynamic target absorption properties are very important for describing the ablation process. The results derived from the transmission studies and etch rates were analyzed theoretically with a two-level model of chromophore absorption. For 248 nm irradiation this model can describe the transmission behavior and the ablation rate. In the case of 308 nm irradiation, it was only possible to match one data set. A good agreement with the experimental transmission ratio does not match the ablation rate and vice versa.