Chemical Modification of Asphalts

In-House ReportProminent among the damages occurring to asphalt cement concrete pavements are cracking and rutting. The occurrence of such damage is dependent upon many factors including the properties of the asphalt, which are, in turn, dependent upon its molecular structure. Experiments to test this hypothesis have been performed; these experiments include the modification of asphalt cements by reacting them separately with maleic anhydride, chromium trioxide and furfural in the presence of hydrochloric acid. Six different asphalts were used in these exploratory reactions. The original and chemically modified asphalts were subjected to laboratory tests to obtain such comparative parameters as penetration-viscosity number, penetration index, limiting stiffness temperature, aging index, complex viscosity, storage modulus, loss modulus, complex modulus and tan delta. These data show that the chemically modified asphalts have potential for use in the highway pavements to help avoid cracking and rutting in such pavements. The adhesion to aggregate by the modified Wyoming pedestal test was performed. The chemical modification of asphalts improves the adhesive bond between asphalt and aggregate in an asphalt mixture implying an increased resistance to stripping. The presence of polar and polymerizing groups in the modified asphalts plays a major role in controlling the adhesion to aggregate. The infrared spectra (IR) and high pressure-gel permeation chromatography (HP- GPC) support this hypothesis

Age-dependent loss of small airways during natural lung aging

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The dilemma of female mate selection in the brown bear, a species with sexually selected infanticide

Because of differential investment in gametes between sexes, females tend to be the more selective sex. Based on this concept, we investigate mate selection in a large carnivore: the brown bear (Ursus arctos). We hypothesize that, in this species with sexually selected infanticide (SSI), females may be faced with a dilemma: either select a high-quality partner based on phenotypic criteria, as suggested by theories of mate choice, or rather mate with future potentially infanticidal males as a counter-strategy to SSI. We evaluated which male characteristics were important in paternity assignment. Among males available in the vicinity of the females, the largest, most heterozygous and less inbred and also the geographically closest males were more often the fathers of the female's next litter. We suggest that female brown bears may select the closest males as a counter-strategy to infanticide and exercise a post-copulatory cryptic choice, based on physical attributes, such as a large body size, reflecting male genetic quality. However, male–male competition either in the form of fighting before copulation or during the post-copulatory phase, in the form of sperm competition, cannot entirely be ruled out