41.It means reorganising them on democratic lines，with governing boards made up of workers and technicians from the trade unions concerned，loyal to the concept of nationalisation as a force for social changes and operating their industry according to anational plan arrived at democratically by the community as a whole.

　　这意味着：要以民主的方式，由有关工会的工人和技术员所组成的管理董事会来改组各项工业。这些工人和技术员作为社会改革的一支力量要忠实于国有化这一观念，同时他们必须按照由作为整体的社会用民主方法制定的全国性计划来管理各工业。(on...1ines，“按照……方针，办法”，作状语。with...concerned介词短语作状语，用来修饰动名词reorganising。Made up of...过去分词短语作定语修饰boards。loyal...changes为形容词短语修饰workers and technicians。as force for social changes是“工人和技术员”的同位语，operating...as a whole为现在分词短语作定语，也是用来修饰workers and technidans。它是与形容词短语loyal。。.是并列关系。arrive at作出(决定)，得出(结论)等。句中arrived at...whole是过去分词短语作定语修饰plan。).

　　42.Thirty-five seconds into the flight，with the solid rockets pumping out maximum power，Challenger—like all its predecessors—was undergoing severe aerodynamic stress.

　　“挑战者”号在其固体燃料助推火箭发出最大推力的推动下，飞行了35秒后，同以前的航天飞机一样，正在承受着巨大的空气动力的压力。(with the solid...复合结构用作状语，有条件意味。).

　　43.A gas，such as steam (water vapor) in the cylinder of asteam engine，has neither deftnite shape nor definite volume-it changes its sshape and also its svolume with change in the shape and volume of the container.、

　　气体，例如蒸汽机汽缸中的水蒸气，既无一定的形状，也无一定的体积。气体的形状和体积是随着容器的形状和体积的改变而变化的。(change...with，“随……而变化”。).

　　44.Their wide use in industry is due not only to these properties but to the fact that the common metals can be shaped into required objects by deformation and by casting into mold，and to the fact that their properties can be greatly altered by alloying with other metals.

　　金属在工业中之所以得到广泛的应用，不仅是由于它们具有上述这些性能，而且还由于普通的金属可以通过加工和铸造而形成所需要的制品，同时还由于金属的特性可通过与其他金属熔成合金而显著地改变。(due to，“由于”。to these properties，to the fact，and to the fact都是due所要求的。句中两个that均引出同位语从句。).

　　45.Newton generalized the idea by supposing that any two particles in the universe gravitate towards each other with a force varying inversely as the square of the distance between them and directly as the product of their masses.46. If an engineer applies aformula or a tabulation or a curve blindly， without knowing its history，its accuracy and the limits of its sapplicability，the results that he obtains will be neither intelligent nor practical.

　　如果一个工程师盲目地应用一个公式、一张图表或一条曲线，而对它的来历、精确度和应用范围却一无所知，那么他所得到的结果既不明智，也不实际。(without...applicability介词短语作谓语applies的条件状语。that引导定语从句，在句中作obtains的宾语。).

　　47.The neutron carries no electrical charge and in some respects acts as though it were composed of a proton and electron combined，with the positive charge of the proton neutralized by the negative charge of the electron.

　　中子不带电荷，并且有点像是由质子和电子结合而成的，质子的正电荷被电子的负电荷中和了。(in somerespects，“在某些方面”，“有点”。act as though，“表现得似乎”。as though引导方式方法状语从句，其谓语常用虚拟语气。句末with引出介词复合结构，对前句的谓语作补充说明。).

　　48.We know that the rate of cooling from above the critical range will greatly change the structure and therefore the properties of any steel.

　　我们知道，从临界温度以上冷却的速率会大大改变任何一种钢的结构，从而会改变其性能。(from above..，“从……以上"，是双重介词。).

　　49.Increasing problems of all kinds with fossil fuel power plants are turning power and utility companiesmoreandmore tOtheuseOfnuclearpoweredelectricgeneratingplants

　　.矿物燃料发电厂所产生的问题日益增多，这就促使电力公司和公用事业公司越来越倾向于采用核动力发电厂。(problem...with，“在……方面产生的问题”，with有表示“范围”。).

　　50.Ever since，people have had difficulty in deciding whether the hovercraft should be ranged among ships,planes，or land vehicles—for it is something in between a boat and anaircraft.

　　从那以后，人们感到很难确定把这种气垫船归为哪一类：船、飞机还是车辆，因为它是一种介于船与飞机之间的交通工具。(in between，“介于两者之间”，作定语修饰something。).