Suppose that the fatigue data for the brass alloy in 8.22 were taken from bendingrotating tests and that a rod of this alloy is to be used for an automobile axle that rotates at an average rotational velocity of 1800 revolutions per minute. Give the maximum bending stress amplitude possible for each of the following lifetimes of the rod: (a) 1 year (b) 1 month (c) 1 day (d) 1 hour
Ecology Mutualism positive/ positive impact. ‘reciprocal exploitation’BOTH MEMBERS BENEFIT—Exploit each other steal from each other. Benefits > costs. Problem: not a lot of experimentation. Food shelter, protection, special services (some adapt to benefit each side). Characteristics: o Degree of partner dependence: Obligatory mutualism association of different species, benefits. One or both cannot survive without the other. Ex termites and gut protozoa (digests wood). Facultative mutualism benefits both species. One or both could survive without the other but do best together. o Degree of physical association between partners: Live together in/on body of other one, very close. Ex microbes and protozoas. Coral algae association. Live apart ex flowering platns and their pollinators. Flowering plants and their seed dispersers. Angiosperms take advantage of vertebrates and vertebrates get food. o Degree of specificity: Nonspecific ‘diffuse mutualism.’ Ex does not matter what pollinates as long as pollinated. Most common. Highly specific mutualism one to one interaction. Incidental benefits coral and fish. Lots of coral for fish, live there because shelter, camouflage, and hide food. Does not impact coral. No special adaptations, just happens to benefit fish. Cheating systems pollination not same species. Chew up seeds and kill plant does not help. Cleaner fish large fish come up and cleaner fish clean off, some fish mimic cleaner fish and will eat the fish that come for cleaning. Classic example of mutualism ant/ acacia tree Southwestern New Mexico. “Bulls horn acacia” has hallow thorns with holes at end. Ants live inside. Shrubs have nectarines that ants eat. Ants protect plant, anything tries to eat it, attacked by ants. Kill zone area around plant and kill all plants trying to grow there so all nutrients go to that plant. Plant provides food, water, and shelter. Ants provide protection to the plant. Parasitism: positive/ negative interaction. Interaction between two species in which one benefits while the other is harmed. Parasite (+) and host (). Considered form of predation, except typically not lethal but can cause problems. Microparasites Macroparasites Small, microscopic. Larger, seen with naked eye. Ex bacteria, viruses, protozoans. Ex ticks, leeches, flat worms, round worms, mistletoe. Short generation time. Longer generation time, >1 year. Develop and mature rapidly in host. Do not multiple in host. Life cycle involves more than one host and carriers. o Host= habitat. Problem: find and access in host. Not all habitat suitable and not found everywhere. Must get on or in host. o Characteristics of parasitism: Infection heavy load of parasites. Disease any state in condition of organism that deviates from normal, ex brain worms. Endoparasites inside body. Ectoparasites outside body, easier to gain access to host but can knock off. o May be a parasite as larvae, adult, or both. Such as maggots. o Parasites of all parts of plants and animals. Highly specialized to an area. o Intermediate host any organism that houses some developmental phase of parasite’s lifecycle. Up to three intermediate hosts required. o Distinctive host organism where parasite reaches sexual maturity, end host. Only one. Sometimes have specific sequence of hosts. o Finding/accessing host: modes of transmission: Direct transfer of a parasite from one host to another by direct contact or through a carrier. Between host to host or carrier. Ex fleas. Carrier bacteria associated with lime disease. Indirect different stages of life cycle in different hosts. Ex brain worm: intermediate snail or slugs, animal eats and end up in lungs and travels to brain. Biggest problem is finding access to host.