Example: If Robinson Crusoe fishes by hand, he can catch 20 fish each week. If he takes a week off to make a net, he can then catch 25 fish a week with the net until it wears out in 10 weeks. In order to avoid starving during the week that he is weaving the net, he can borrow 10 fish from Friday, on the condition that he pays back the 10 fish plus an extra 5 fish. The cost of the net is the 20 fish that he gave up by not fishing for a week plus the 5 extra fish paid to Friday, or 25 fish. The gross marginal productivity of the net (the total addition to productivity that it contributes) is (5 fish per week)•(10 weeks) = 50 fish. The net marginal productivity of the net (the total addition to productivity that it contributes, less its cost) is (50 fish) – (25 fish) = 25 fish.
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Fish • Most fish reproduce by laying eggs, though some fish, such as great white sharks, give birth to live babies called pups • Fish use a variety of low-pitched sounds to convey messages to each other. They moan, grunt, croak, boom, hiss, whistle, creak, shriek, and wail. They rattle their bones and gnash their teeth. However, fish do not have vocal chords. They use other parts of their bodies to make noises, such as vibrating muscles against their swim bladder • Saltwater fish need to drink more water than freshwater fish. Since seawater is saltier than the liquids in a fish’s body, water inside the fish is constantly flowing out. If they didn’t drink to replace the lost water, saltwater fish would dry up like prunes.
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Dining Philosophers • • Initially state[1] for all is set to thinking Philospher 1 wants to eat: Pickup[1] – state[1] = hungry – Test[1] • State[1] == hungry && state[0] != eating && state[2]!=eating : TRUE • Thus state[1]=eating • Self[1].signal() does nothing • Philosopher 2 wants to eat – State[2] = hungry – Test[2] • State[2] == hungry && state[1] != eating && state[3]!=eating : FALSE • Self[2].wait() • When philosopher 1 is done invokes putdown[1] – – – state[1] test(0)forks it test(2)forks it = thinking; if philosopher 0 will be put into if philosopher 2 will be put into is hungry and its neighbors are not using their eating state and signaled is hungry and its neighbors are not using their eating state and signaled Ref: http://userhome.brooklyn.cuny.edu/irudowdky/OperatingSystems.htm & Silberschatz, Gagne, & Galvin, Operating Systems Concepts, 7th ed, Wiley (ch 1-3)
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31. Pigeon Guillemot eating fish
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Hypotheses Testing: Ha3 Activity-specific Items Fish targeted Items Trout I’m just as happy if I don’t keep the fish I catch ………………… 3.897 I’m just as happy if I release the fish I catch ………………………. 3.943 To obtain fish for eating, and not for sport ……………………...1.697 For the sport of fishing, not to obtain food to eat …………………. 3.632 For the experience of the catch………….3.617 Bass F p 4.417 70.654 0.000 4.450 68.924 0.000 1.306 44.650 0.000 4.137 38.307 3.989 27.854 0.000 0.000 _____________________________________________________________________________________ When I go fishing, I’m just as happy if I don’t catch a fish …………. 3.097 A fishing trip can be successful even if no fish are caught …………….3.854 3.010 1.352 0.245 3.875 0.102 0.749
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Example: big fish eats little fish A big fish, M = 5 kg swimming at 1 m/s eats a little fish, m = 1 kg that is at rest. What is the speed of the big fish just after eating the little fish? • The two fishes form a system and their momentum before the “interaction” is the same as their momentum after the “interaction”. • Momentum before = M Vbefore + m (0) = 5 kg x 1 m/s • Momentum after = (M + m) Vafter = (5 + 1) Vafter •  5 kg m/s = 6 Vafter  Vafter = 5/6 m/s 6
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Problem 34.17 A small tropical fish is at the center of a water-filled (n=1.33) spherical fishbowl 28cm in diameter. a) Find the apparent position and magnification of the fish to an observer outside the bowl. b) A friend advised the owner of the bowl to keep it out of direct sunlight to avoid blinding the fish, which might swim into the focal point of the parallel rays from the sun. Is the focal point actually within the bowl? For part a) consider the fish to be the light source, and calculate the image position for light rays exiting the bowl. Magnification can be found from this formula: m  na di nb do m  1. 33(  14cm) 1. 33 1(14cm) We will be using this formula: na nb nb  na   do di R Here is the given information: The fish appears larger by a factor of 1.33 na 1. 33; nb 1; do  14cm; R   14cm 1. 33 1 1  1. 33    di   14cm 14cm di  14cm This radius is negative because the center of the bowl is on the same side as the light source (the fish) A negative value for S’ means the image is on the same side of the interface as the object (i.e. inside the bowl in this case). So the observer will see a virtual image of the fish at the center of the bowl. Prepared by Vince Zaccone For Campus Learning Assistance Services at UCSB
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Rules in Detail: Fish Rules If the current cell contains a fish:  Fish live for 10 generations  If >=5 neighbors are sharks, fish dies (shark food)  If all 8 neighbors are fish, fish dies (overpopulation)  If a fish does not die, increment age 12
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Dining Philosophers void pickup(int i) { state[i] = hungry; test[i]; if (state[i] != eating) self[i].wait(); } void putdown(int i) { state[i] = thinking; // test left and right neighbors test((i+4) % 5); test((i+1) % 5); } void test(int i) { if ((state[i] == hungry) && (state[(i + 4) % 5] != eating) && (state[(i + 1) % 5] != eating)) {state[i] = eating; self[i].signal(); } } } end of monitor dp // philosopher i can set its state variable to eating only if the two neighbors are not eating Ref: http://userhome.brooklyn.cuny.edu/irudowdky/OperatingSystems.htm & Silberschatz, Gagne, & Galvin, Operating Systems Concepts, 7th ed, Wiley (ch 1-3)
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WHY EATING DISORDERS ARE A PROBLEM “A Study conducted by Cornell University found that 40% of male football players surveyed engaged in some sort of disordered eating behavior. -Newsweek, 1994 “The average woman is 5”4’ and weighs 140 pounds. The average model is 5”11’ and weighs 117 pounds. Most fashion models are thinner than 98% of American women.” -National Eating Disorder Association “It is estimated that currently 11% of high school students have been diagnosed with an eating disorder.” -ANAD.org “1 in 5 women struggle with an eating disorder.” -NIMH “42% of 1st-3rd grade girls want to be thinner” - International Journal of Eating Disorders
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• Disordered Eating and Eating Disorders • Disordered eating behaviors are common and widespread – Restrictive dieting, skipping meals, binge eating and purging, laxative abuse, etc. – May occur in response to emotional stress, an upcoming athletic event, concern about personal appearance, etc. – Disordered eating behaviors may or may not develop into a full-blown eating disorder ©McGraw-Hill Education.
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