Elongation studies exposure

Our study shows that UV exposure of prion protein, P2-microglobulin and a-synuclein leads to loss of ability of these proteins to form amyloid fibrils de novo. However, they retained the ability to elongate the fibrils when provided with preformed fibrils as seeds. Thus, UV exposure selectively compromises the ability to nucleate fibril growth. 

Several studies look at the crosslinking of PVC compounds containing CaCO,. Exposure of a PVC compound to y-radiation will change its properties. Properties affected include tensile strength and Young modulus which are increased and elongation which is decreased. Figure 11.1 shows that the presence of calcium carbonate had minimal influence on crosslink density. Similarly, calcium carbonate did not influence the performance of the crosslinker (trimethylol propane trimethacrylate). 

Low-Density Polyethylene. The data from outdoor weathering are summarized In Figure 1. The low-temperature brittleness (LTB) measurements show that a well-dispersed carbon black of > 1% concentration and < 35 millimicrons (mu) particle size Is necessary for maximum resistance to photo-oxldatlon. The results from elongation measurements agree with those found for LTB, as would be expected, since both measurements reflect the notch sensitivity of polyethylene to micro cracks caused by photo-oxldatlon. Accelerated weathering studies on these compounds have been reported previously (2) and Indicate the same ranking as found in outdoor exposure. 

Reactor exposure causes decrease in elongation at break and increase in the modulus of elasticity due to crosslink formation [434]. High doses are, however, required to produce appreciable change. 7-Irradiation gives decreased tensile strength and elongation at break for nylon 6 and nylon 6, 6 [433] (Fig. 47). The dynamic mechanical properties of nylon 6, 6 were studied by Sauer et al. [436] after neutron irradiation. Rubber-like behaviour was observed for temperatures above the main softening temperature. 

Despite many studies of the effects of photooxidation on mechanical properties (such as Young s modulus, tensile strength, ultimate elongation, etc.. ..), there is very little information about these effects on fatigue life. For that reason, we studied the fatigue life of LDPE films as a function of UV exposure. The results are shown in Fig. 2 where logNp (Np being the number of cycles sustained before failure) is plotted vs. time of UV exposure. In this case the strain amplitude is 8% and the frequency (oj) is 10 cycles/mln. 

Same material but containing 0.1% of a photostabilizer (Cyasorb UV 3346, American Cyanamid Co.) was also studied in a similar experiment designed to obtain a direct activation spectrum of the material [133]. After 1400 h exposure in an Atlas Ci 65 weatherometer, the samples showed measurable changes in both elongation at break as well as the tensile strength. Maximum effectiveness was found at A = 335-355 nm. 

An important aspect in all drug delivery is the toxicity of the drug as well as that of the drug carrier. Therefore, toxicity has to be assessed also for microemulsion formulations. In microemulsion systems, the main concern regarding toxicity has to do with the cosurfactants used. For example, the majority of the work on the pharmaceutical application of microemulsions has involved the use of short- or medium-chain alcohols, e.g., butanol. In a range of studies it has been shown that these cause toxic side effects. For example, inhalation studies of the toxicity of 1-butanol, 2-butanol, and / -butanol in rats showed a dose-dependent reduction in fetal weight [56]. Furthermore, aqueous solutions of ethanol, propanol, and butanol were shown to result in elongated mitochondria in hepatocytes after 1 month of exposure [57]. (In addition to the toxicity aspects of these alcohols, microemulsions formed in their presence are often destabilized on dilution of the continuous phase.) Furthermore, many studies so far have involved aliphatic or aromatic oils, such as hexane or benzene, which obviously are unsuitable for pharmaceutical use. Moreover, ionic surfactants could in themselves be toxic and irritant [58]. 

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