首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Cities are often described as being alive. A nice metaphor, but does it mean anything? And, if it does, can town planners and bi
Cities are often described as being alive. A nice metaphor, but does it mean anything? And, if it does, can town planners and bi
admin
2016-10-21
41
问题
Cities are often described as being alive. A nice metaphor, but does it mean anything? And, if it does, can town planners and biologists learn from one another? Steven Strogatz, a mathematician at Cornell University, wrote last year that Manhattan and a mouse might just be variations on a single structural theme. His point was that both are, in part, composed of networks for transporting stuff from one place to another. Roads, railways, water and gas mains, sewage pipes and electricity cables all move things around. So do the blood vessels of animals and the sap-carrying xylem and phloem of plants. How far can the analogy be pushed?
Peter Dodds of the University of Vermont draws a particular analogy between the blood system and a suburban railway network. The commuter-rail system of a city ramifies from the centre. The farther out you go, the sparser it is. By analogy, Dr. Dodds predicted, the network of capillaries would not be as dense in large animals as it is in small ones. They, too, branch ultimately from a central source — the heart. Surprisingly, no one had looked for this before, but in a paper published recently in Physical Review Letters Dr. Dodds shows that this does indeed turn out to be the case.
Dr. Dodds’s calculations overthrow a 70-year-old rule of thumb which is known as the 3/4 law of metabolism. This suggests energy expenditure is proportional to body mass raised to the power of three-quarters. That a mouse expends more energy per gram than an elephant does is well known. But Dr. Dodds’s calculations show that metabolic rates must fall off faster than had previously been believed as animals get bigger because less glucose than thought is being transported by the smaller than predicted capillary network. The law needs to be adjusted to something more like two-thirds.
Two other studies published in the same volume similarly overthrow conventional wisdom about plants. Traditionally, biologists have celebrated the trunk, branch and twig system of a tree as no accident. Many mathematical formulas have suggested it is the best, least wasteful way to design a distribution network. But the very end of such a network, the leaf, has a different architecture. Unlike the xylem and phloem, the veins in a leaf cross-link and loop. Francis Corson of Rockefeller University in New York used computer models to examine why these loops exist.
From an evolutionary point of view, loops seem inefficient because of the redundancy inherent in a looped network. Dr. Corson’s models show, however, that this inefficiency is true only if demand for water and the nutrients it contains is constant. By studying fluctuations in demand he discovered one purpose of the loops: They allow for a more nuanced delivery system. Flows can be rerouted through the network in response to local pressures in the environment, such as different evaporation rates in different parts of a leaf.
The leaf, then, is a resilient distribution network — one whose principles could be applied to, say, electricity grids. Next time your power is cut off because a tree has fallen on the cable, remember that.
Which of the following statements is INCORRECT?
选项
A、The farther out capillaries go from the heart, the sparser they are.
B、Cities are described as being alive as plants and animals.
C、Like blood vessels, xylem and phloem can move things around.
D、The commuter-rail system is dense at the centre.
答案
A
解析
推断题。从文章第二段看似乎A正确,但By analogy,Dr.Dodds predicted,thenetwork of capillaries would not be as densein large animals as it is in small ones指出这个结论仅仅是一个推论,还没有得到科学的证实,故A错误。B在开头第一句,文章后面讲了动植物的类比,正确。从第一段中Roads,railways,water and gas mains,sewage pipes and electricity cables all movethings around.So do the blood vessels ofanimals and the sap-carrying xylem andphloem of plants可以判断C正确。从第二段中The commuter—rail system of a cityramifies from the centre.The farther out yougo,the sparser it is可以推断D正确。
转载请注明原文地址:https://kaotiyun.com/show/XA7O777K
0
专业英语八级
相关试题推荐
______isthesecondlargestcityinCanadaandisalsothesecondlargestFrench-speakingcityintheworldbehindParis.
Ofthefollowingwriters,whoisanimportantfigureintheEnglishRenaissance?
Fromaveryearlyage,perhapstheageoffiveorsix,IknewthatwhenIgrewIshouldbeawriter.Betweentheages【M1】______
Thefollowingwritersallbelongtothe"AngryYoungMen"EXCEPT
"YoushouldspendmoretimeonEnglish"isa(n)
SomepeoplehavedrawntheconclusionfromBowlby’sworkthatchildrenshouldbesubjectedtodaycarebeforetheageofthree
RichardNixonresignedbecauseof
HowtoApproachDiscursiveWriting?Howtoimprovetheeffectivenessofstudents’writing?Therearesixstageswhichshould
HowtoApproachDiscursiveWriting?Howtoimprovetheeffectivenessofstudents’writing?Therearesixstageswhichshould
DonnyDeutschemphasizestheimportanceof______asthekeytosuccess.Alittlehatredisametaphortoshowyouneedtobe____
随机试题
焊条的组成是怎样的?
催化裂化催化剂的主要性能是什么?
创伤伤口的收缩是在
乳牙列形成期是指
厂房一层火灾失控时,对正在五层工作的员工来说,下列做法中,错误的是()。
我国基金管理人编制的基金财务报告可以不及时公告,但必须向证监会报告。()
国务院旅游主管部门是旅游发展规划评估的组织主体。()
加涅的学习结果分类中不包括()
酸雨是指pH值低于5.6的大气降水,包括雨、雪、露、霜,造成酸雨的主要原因是大气中的()。
VisualBasic控件一般都规定一个默认属性,在引用这样的属性时,只写对象名而不必给出属性名。默认属性为Caption的控件是( )。
最新回复
(
0
)