Click for next page ( 32


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 31
- e P4 H :t U] ~ ~ ~ ~ a H _' ~ ~ Pip so= O E~X Ed- ret O O O O O O m P: V A 3 '= ~U] _ U] ~ ~ ~ ~a ~ ~ O ~H N ~ U1 ~ lay ~ ~O = -~ - ~ Hi_ O U] -- ~ ~O ~ ~= W ~ ~ U3= O OX W ~ a tic 0 ~ :~:- 0 ~ 0 to ~ ~ t: 0 ~ - zm~ ~ Ed ED H S O P ~ tn x: ~ ^ q4 044 ~ 0 U O m ~ ~ ~n P ~ 0 ~ P ~ ~= m ~ ~ D O = - P4O 1 16 IB O E~ ~ ~= 1 a, a ~X~ P: ~= P~ ~ m ~ ~m P am ~ ~ CO~ -= ~ _ z H ~U ~ O E. c~ O Z ~- 14 a)0 ~ ~ ~ Q r.~ t. ., 31 tn u .,' . C) o H P: N U) U] U) U U] ~ 65 Q _1 U U ~ ~ ~_ .,~ _1 ~ In ~_ ~R ~4 U] - ~ Q _I 4) .,' P. U1 O ~ O I S" eq ~_ O O ~ ~ O O ~ e-- ~ ~ ~= O cn Q - ~n Q o X 0 000000 ~D o 0 0= ~0 0 0 ~ 1 ~D O O ~ - 0 0 1 n ~ ~ ~ 0 0 0- 0 - ~~ ~ 0 B 0 0 ~ ~ u ~ p ~p o ~0 ~ 0 0 A ChA 0 P. ~ ~ ,l~ ~ 0 0 . '., U 0 .. 0 ~ ~ 0 - 0 d ~ ,4 1 ., ~.,4 0 0 0 " ~JJ 0 ; dJ 1 ~ '' OJ3~ 0 U 0 ~ O ~ - o. 0 0 ~ 'U 0~ 0 ~ 0 0" 0 ol~ 0 ~0. ~U] U d~ ~ 0 ~ ~ 0 - ~ ~0 0 - ~ ~ - ~ ~PtO O O =0 ' Pt 0 ~0 ~ U ~d 0 0 - U ~ - ~P n" 0 0 CR~ ~O - 0 e0 S .,' "C m ~ n: 0 U 3 ~c m O ~ 3 - O ~ u, O 1 o.~ I a 0 ~_ a 1 O: f 0 ~ :Z O ~H Q. U U. - U] ~ 3 X U ~ U] W U ~ C o ~ ~ ~ w :> ~ o o o ~ a: ~ m ~rl ~ ~ ~ 3 .. ~ Z O o z 4t 1 ~ . Q o U] S ~4 o U] U U 0 S N .,1 Ql _I Z; E~ O ~q IB ~n U] U] 0 Q 0 Q ~ o O X ~ ~ ~ ~ _I ,1 ttS _ O U ~ ~_ U _I ~ ~ IO u, .,. ~ S ~ ~ ~ 0 ~ ~ O 4} O S X E~ - 0 _I U ,' o N . 0 U _ ._ ~ .,' ~ ~5 0 ~ . - ~0 a ~ W 54 :> P: ~ W ~_ U] ~ ~tn U] 0 ~ ~Q W H P: ~ ~O O P: ~ W-e X m~ :~: ~q~ ~ 0 . ~z 0 U, o ~: w H W U] z o E~ ~: E~ ~: o P4 z P; E~ m ~: p ~m _ U] _I 1 0 ~ E~ m n: m U] ~ a:a ~ 0 Z,C H U] U] ~ ~:W U :~ a- ll ~i Q al .4 > 0 al ~ U > R ~R ~ .~ ~ P. O O U S~ ~ ~ O 0 ='~ s~ 0 0 0 0 U O ~n 0 u ~C) ~ 0 U O ~ ~ ~0 U O ~ 0 ~= Q 0 ~1 U ~ 0 R 0 0 U] ~ U ~ ~ ~ ~_ eq ~ ~= O c~ ~ ~ ~ ~ U U ~ ~ U ~ 0= U~ - 00 00 0 ~n 0 0 O O 0 0 0 0- 0 0 0 0= ~ ~ ~ ~ S - - ~- - ~ O o

OCR for page 31
32 ~V ~I ~ ~h ~ ~ ~ ~. ~ ~- Q Was ~ - O ~- -- - .- :> ~ XU ~ V ~ ~O ~h ~1 ~U h en o4 ~ Its ~ ~ 0 ~ ~ I ~ ~ ~ ~ O O :Z ~ ~ h ~ ~ ~ _ ~ ~ ~ ~ ~- ~ O 0 ~o4 Ot)U1 ~ ~ ~Oar H h ~O ~ ~ -1 ~-- ~ ~ ~ ~ ~ ~ ~ ~ ~ _ E~ ~O S - ~ U tns p: - u, ~ os z ~ ~ 0 0 ~S U~ ~ ~ ~ a ~ ~ ~ - 0= ~ ~ ~= ~ O O ZX U) Ul 0 ~ ~ h h O ~ ~ ~ O ~ ~ ~ - ~ ~ - 1 U .. . e X ~ ~ ~ ~ h S E ~-o~=~= U1S = ~= - ~ ~ ~ ~ U O ~ U ~; O O ~ O O_ o oooooO ~Z s0000 ~Z O 000 000 ~ O ~ _ ,' - 4 _ 44 ,1 U IB ~ - O ~ O O O ~- ~ c O ~0 0 h~ h~ OX h O 3 ~ O~ c~ ~ a) ~ ~ ~ - ~ h S a' ~ ,C, O X ~ =,- - fT~ S ~ ,[~- - O~ ~ h h C: ~ ~ O = - n O=- ~ ~ V -4~ U~ ~ ~ o O ~0 ~ G) :~4 h O ~ ~ O S O ~'~ O N >~ - ~ V ~ ~ ~.- V _I ~-~1 R ~ O ~ c h O O O P4Q ~ h ~ h :~ -V ~ ~h 3 P. O O O O m P: m U) 1 o E~ 1 m m CO R z o <,: j C ~1 h _ Ul ,' i) ~C -rl 3 ~ C `4 ~ O -: O V C O O H ,q, E~ o C) E~ nd P4 U] P. ~ ~- C) ~ Z~. ~ U] U] ~: U ~ H _I :> P: ~ OW ~ O ' ~U] ~c cn W o w ~; w E~ ~: ~: E~ c) w u] p w o 1 E~ ! : I ~ E~ w 1 1 W 1 ~ 1 `4 H U] I ~ 1 Ce) I H ,~ W ~. U] U] UB 1 W ~ O ~ m ~= O: H 3 ~ I m ~ 1 3 W ~m 00 U] ~- U, S JJ 3 S ~n h ,' h .,. h U I0 ~h Q) ~ O - q4 X H ~ ~ - ~ ~n .,~ - u4 a: H o P. U, H z z H 3 o . - V s U] ~ cn ~ ~ ~ h G) O--l R tP=SX ~ 0 ~ h O h U] ~ ~ ~ ^ P4 Q'~J R ~u U] h _I ~ ~ U1 0 ~ ~ U V S ~ ~ ~ ~ ~ U~ ~ a_ .,~ ,~ ~ h U] ~ h h~ ~ ~ oS~ ~ ~ ~S 0~ O ~P4U O O O O O O O a `~`, V ~ ~ - .,. ~ ~ -,1 :- ~ h V -R ~O :>' ~ ~ U Z ~- 0 n5 ~ ~ O ~ V H O S ~ " h ~ ~ ~ ~ O ~ ~ `240 ~ ~ ~ ~ - ~; S ~= ~ ~ O `~ _ p4 U] ~ S 0 - ~XX~ ~ ~S . 0 ~m a) ~ ~ ~= X u) P43~ U' O ~ ~ V . a ~S~ 0~0 O :n-Z O O O O O O

OCR for page 31
33 ~ Bock '~0 0 ~ -= ~=.e -~ I .= 0 ~ 0 =~= 0 al u ~ ~ ~ ~ ~ ~ use 0 U) ~ ~ U O ~ d ~= ~ ~ ~ ~ 0~ ~ 'A Ul ~ ~ ~ ~ d ~ 'a ~ ~ ~ ~ U ~ ~ ~ (~rV' ~ ~ ~ un ~ ~ . ~ ~1 o 0 ~ ~ ~ ~ o ~ ~ ~ ~ ~ ~ o~ I U1 ~ ~ ~ ~H ~ - ~ ~ 0 ~ ~ ~0 ~ ~ ~ ~ ~ Van ~ ~ ~ ~ ~ ~ O .~ a~ O ~ ~ U 0 d ~ U U :^ ~ ~ - ~H o ~ ~ ~ ~ ~ ~O ~ O = ~a ~ - O ~ ~ ~ . - ~ 0 d ~ 0 0 ~O us a n=~ 0 ~ ~ ~ 0 ~ 0 n - = H ~- ~ ~H d O ~ ~ 0 U ~ ~ ~ ~ ~ ~ ~ ~ ~ d 8 ~,, ~' va u ~:! ~ E- ~ r~ ~ U > ~ ~a q 6~ ~ ~ U ~3 r ~tU 8 ~ << aO) ~o ~Z~ ~ ~= ~=.t ~ P:=o U1 ~00 ~'0~= ~30 ~ O ~ O -~`' ~- ~= 0= ~ ~ 1 ~ :>~ U ~>~ ~ ~ O ~ ~ ~ X ~ ~ ~ ~ O ~ ~ R~ tO ~ ~ ~ 0 ~ ~R OU] ~ ~ ~ O 0~ U ~ ~ ~ a H O O H ~5 ~5 ~ a ~ - 0 0 0 0 0 ~ ~H 0 H d R U) ,' n n cu J CU U - U ~ ~i _ ~ ) .o ~ U] ) ~ O i O ,._' - '> 1 ' ~ tn E~ (U ~- ~