新托福阅读背景知识精选整合（通用7篇）由网友“吴杰民”投稿提供，以下是小编为大家整理后的新托福阅读背景知识精选整合，欢迎阅读与收藏。
篇1：新托福阅读背景知识精选整合
What is p53?
After the identification of the p53 protein and the subsequent cloning of p53 genes from several species, early observations suggested that p53 may function as an ontogeny, because over expression of p53 appeared to cause monogenic transformation of cells. In the late 1980s, however, several critical discoveries defined the normal function of p53 to be anti-monogenic. Wild-type p53 genes, when introduced into cells, were found to be growth suppressive. The screening of DNA from colon cancer patients revealed that p53 mutations occur with unusually high frequency in tumor tissue, an observation that was extended to most of the other major forms of human cancer. Indeed, members of Li-Freemen cancer-prone families were shown to carry germ-line p53 mutations. The importance of these observations was underscored by the finding that mice that are homozygous null for p53, although developmentally competent, are highly predisposed to tumors.
The functional character of the p53 protein was determined by experiments showing that p53 contains a strong transcriptional activation domain within its amino terminus and that it is a tetramer, sequence-specific DNA-biding protein with a defined cognate binding site containing two copies of the 10-mer (5'-RRRCA/TT/AGYYY-3'). Although the p53 protein acts as a transcriptional activator of genes containing p53-binding sites, it is also capable of strongly inhibiting transcription from many genes lacking p53-binding sites. Several monogenic DNA viruses express viral gene products that associate with and inhibit the trans-activation function of p53, notably SV40 large T antigen, the adenovirus E1B 55-kD protein, and the E6 protein of monogenic forms of human papillomavirus (HPV E6). In cells, p53 can associate with a 90-kD protein, identified as the product of the mdm-2 ontogeny, which is amplified in some types of tumors. When bound to mdm-2, p53 can no longer function as an activator of transcription.
P53 plays multiple roles in cells. Expression of high levels of wild-type (but not mutant) p53 has two outcomes: cell cycle arrest or apoptosis. The observation that DNA-damaging agents induce levels of p53 in cells led to the definition of p53 as a checkpoint factor, akin, perhaps, to the product of the fad9 gene in yeast. While dispensable for viability, in response to geotaxis stress, p53 acts as an “emergency brake” inducing either arrest or apoptosis, protecting the genome from accumulating excess mutations. Consistent with this notion, cells lacking p53 were shown to be genetically unstable and thus more prone to tumors.
(中文版)
p53是存在人体细胞内的一种抗癌白质，它有抑制细胞生长及维持遗传物质完整性的功能。事实上，半数以上的癌症细胞内都有p53的突变，可见其在细胞生长控制上扮演了重要的角色。在正常状况下，p53的半衰期约只有30分钟，相当不稳定;然而当细胞经紫外线，离子化射线(如X光，伽傌照射)，或当细胞缺氧、缺养时，p53被活化，同时它的稳定性提高，造成细胞内的p53大量增加，除了上述刺激外，化学治疗上常用的药物也有同效。这种p53的活化与增加常导致两种可能的结果：一是细胞长停止在G1或G2期;另一是细胞采自杀行为(apoptosis)而死亡。细胞由此得以修补损坏(前者)，或过度受损的细胞得以从人体除去(后者)。这种依赖p53的“自卫措施”在一些细胞中常因p53的突变而失去功能，使得这些有“缺陷”的细胞能继续不受控制的生长分裂，导致突变的累积和癌症的生长。
虽然环境因子影响p53活性及稳定性的事实已知已久，其间的分子机转仍不清楚。蛋白质的磷酸化(phosphorylation)一向被认为在讯息传递上扮演重要的角色。事实上，经由我们及其他实验室的研究发现，p53在经过紫外线，伽傌射线照射后，其N端的数个胺基酸(第15，20，33，37)有磷酸化的现象。这种磷酸化发生极为快速，几乎是在照射后数分钟内即已产生，而持续多久则视胺基酸位置、刺激型态，及细胞种类而异。至于这些磷酸化与p53的反应之关联性则仍有待证明。最近我们发现有两个在细胞分裂(Cell cycle)的检查点(checkpoint)上扮演着重要调控功能的磷酸化酵素(kinas) hCHK1，CHK2可以有效的磷酸化p53。有趣的是，磷酸化的胺基酸中包括了那些可以被紫外线、伽傌线引起的位置，即第15，20及37胺基酸。我们正着手研究可能的CHKs的上游分子及p53在CHKs磷酸化后功能之变化。此外， 不同的环境因子与p53联系的方式可能各异，有些可能透过磷酸化以外的方式进行。 我们希望能先定出p53序列中与环境因子互动有关的区域(domain)，再由此找出与调节p53稳定性有关的机制及分子。
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篇2：新托福阅读背景知识整合
关于钟乳石的形成
石灰岩洞中的钟乳石、石笋是怎样形成的
桂林是世界闻名的风景区，山奇水秀，风景美丽，因此自古就有“桂林山水甲天下”之称。桂林除山水美之外，还有更具特色的石灰岩洞，七星岩是比较有代表性的溶洞。洞内到处悬垂着美丽的钟乳石，有的像累累的果实，有的像盛开的花朵。与之相对应的石笋拔地而起，一个个像春天从地面下“冒”出来的竹笋。
那么这些奇丽的钟乳石和石笋是怎样形成的呢?
原来“盛产”钟乳石和石笋的溶洞都是石灰岩构成的。洞顶有很多的裂隙，每一处裂隙里都有水滴渗透出来。每当水分蒸发掉后，那里就会留下一些石灰质的沉淀，日积月累，天长日久洞顶上的石灰质愈积愈多，终于形成了乳头。以后，乳头外面又包起一层石灰质，以至越垂越长，就形成了姿态万千的钟乳石。
石笋其实就是钟乳石的孪生兄弟。当洞顶上的水滴落下来时，石灰质也在地面上沉积起来，就这样石笋对着钟乳石向上长起来，若是说钟乳石是“兄长”，那石笋就是“孪生弟弟”了。
而石笋底盘大，本身比较稳定不易折断，所以它比钟乳石的生长速度还要快，还要粗壮呢。
篇3：新托福阅读背景知识整合
The Civil War
Causes of the war
The American Civil War was fought between the northern and southern states from 1861 to 1865. There were two main causes of the war. The first was the issue of .lavery: should Africans who had been brought by force to the US be used as slaves. The second was the issue of states' rights: should the US federal government be more powerful than the governments of individual states.
The North and South were very different in character. The economy of the South was based on agriculture, especially cotton. Picking cotton was hard work, and the South depended on slaves for this. The North was more industrial, with a larger population and greater wealth. Slavery, and opposition to it, had existed since before independence (1776) but, in the 19th century, the abolitionists, people who wanted to make slavery illegal, gradually increased in number. The South's attitude was that each state had the right to make any law it wanted, and if southern states wanted slavery, the US government could not prevent it. Many southerners became secessionists, believing that southern states should secede from the Union (= become independent from the US).
In 1860, Abraham .incoln was elected President. He and his party, the .icans, were against slavery, but said that they would not end it. The southern states did not believe this, and began to leave the Union. In 1860 there were 34 states in the US. Eleven of them (South Carolina, Mississippi, Florida, Alabama, Georgia, Louisiana, Texas, Virginia, Arkansas, Tennessee and North Carolina) left the Union and formed the .erate States of America, often called the Confederacy. Jefferson .became its President, and for most of the war d, Virginia, was the capital.
Four years of fighting
The US government did not want a war but, on 12 April 1861, the Confederate Army attacked .ort Sumter, which was in the Confederate state of South Carolina but still occupied by the Union army. President Lincoln could not ignore the attack and so the Civil War began.
Over the next four years the Union army tried to take control of the South. The battles that followed, .hiloh, Antietam, .ull Run and Chickamauga, have become part of America's national memory. After the battle of .ettysburg in 1863, in a speech known as the .ettysburg Address, President Lincoln said that the North was fighting the war to keep the Union together so that '...government of the people, by the people, for the people, shall not perish from the earth'. In the same year he issued the .mancipation Proclamation which made slavery illegal, but only in the Confederacy.
Slaves and former slaves played an important part in the war. Some gave information to Union soldiers, because they knew that their best chance of freedom was for the North to win the war. Many former slaves wanted to become Union soldiers, but this was not very popular among white northerners. In spite of this opposition about 185000 former slaves served in the Union army.
Women on both sides worked as spies, taking information, and sometimes even people, across borders by hiding them under their large skirts.
In the South especially, people suffered greatly and had little to eat. On 9 April 1865, when the South could fight no more, General Robert E .ee surrendered to General Ulysses S .rant at .ppomattox Court House in Virginia. A total of 60 people had been killed and many more wounded.
The war was over but feelings of hostility against the North remained strong. John Wilkes .ooth, an actor who supported the South, decided to kill President Lincoln. On 14 April 1865 he approached the President in Ford's Theatre in Washington and shot him. Lincoln died the next morning.
The killing of President Lincoln showed how bitter many people felt. The South had been beaten, but its people had not changed their opinions about slavery or about states' rights. During the war, the differences between North and South had become even greater. The North had become richer. In the South, cities had been destroyed and the economy ruined.
After the war the South became part of the United States again. This long, difficult period was called Reconstruction. The issues that had caused the war, slavery and states' rights, still had to be dealt with. The issue of slavery was difficult, because many people even in the North had prejudices against Blacks. The new state governments in the South wanted to make laws limiting the rights of Blacks, and the US government tried to stop them. Between 1865 and 1870 the 13th, 14th and 15th .mendments to the .onstitution were passed, giving Blacks freedom, making them citizens of the US and the state where they lived, and giving them, in theory, the same rights as white Americans.
Many northern politicians went to the South where they thought they could get power easily. These northerners were called .arpet-baggers. Both carpet-baggers and southern politicians were dishonest and stole money from the new governments, which hurt the South even more.
In 1870 the last three southern states were admitted to the Union again, and in 1877 the northern army finally left the South. The war lasted four years, but efforts to reunite the country took three times as long.
Effects of the Civil War
Differences between North and South are still strong. In the South the Confederate flag is still often used, and the state flags of .eorgia and .ippi were made to look similar to it. The state motto is Adams jury nostra defender, which is Latin for 'We dare to defend our rights'. The Civil War helped to end slavery, but long afterwards Blacks were still being treated badly, and race relations continue to be a problem. The South was so angry with the .cans, the party of Lincoln and Reconstruction, that southerners voted .atic for a century. The war showed strong differences between parts of the US, but many people believe that the most important thing it did was to prove that the US is one country.
篇4：新托福阅读背景知识精选整合
About 纳米材料及其应用
纳米技术在生物工程上的应用
众所周知，分子是保持物质化学性质不变的最小单位。生物分子是很好的信息处理材料，每一个生物大分子本身就是一个微型处理器，分子在运动过程中以可预测方式进行状态变化，其原理类似于计算机的逻辑开关，利用该特性并结合纳米技术，可以此来设计量子计算机。美国南加州大学的Adelman博士等应用基于DNA分子计算技术的生物实验方法，有效地解决了目前计算机无法解决的问题—“哈密顿路径问题”，使人们对生物材料的信息处理功能和生物分子的计算技术有了进一步的认识。
虽然分子计算机目前只是处于理想阶段，但科学家已经考虑应用几种生物分子制造计算机的组件，其中细菌视紫红质最具前景。该生物材料具有特异的热、光、化学物理特性和很好的稳定性，并且，其奇特的光学循环特性可用于储存信息，从而起到代替当今计算机信息处理和信息存储的作用。在整个光循环过程中，细菌视紫红质经历几种不同的中间体过程，伴随相应的物质结构变化。Barge等研究了细菌视紫红质分子潜在的并行处理机制和用作三维存储器的潜能。通过调谐激光束，将信息并行地写入细菌视紫红质立方体，并从立方体中读取信息，并且细菌视紫红质的三维存储器可提供比二维光学存储器大得多的存储空间。
到目前为止，还没有出现商品化的分子计算机组件。科学家们认为：要想提高集成度，制造微型计算机，关键在于寻找具有开关功能的微型器件。美国锡拉丘兹大学已经利用细菌视紫红质蛋白质制作出了光导“与”门，利用发光门制成蛋白质存储器。此外，他们还利用细菌视紫红质蛋白质研制模拟人脑联想能力的中心网络和联想式存储装置。
纳米计算机的问世，将会使当今的信息时代发生质的飞跃。它将突破传统极限，使单位体积物质的储存和信息处理的能力提高上百万倍，从而实现电子学上的又一次革命。
有关纳米技术
华人科学家：美国纳米技术应用研究四大热点
正在美国从事纳米技术研究的华人青年科学家崔屹博士17日接受新华社记者采访时表示，美国纳米技术的应用研究目前正在半导体芯片、癌症诊断、光学新材料和生物分子追踪等四大热点领域快速发展，其中在芯片和癌症诊断领域的应用可望在内出现划时代的突破。
崔屹说，在癌症研究领域，利用纳米技术制成的传感器可望使各种癌症的早期诊断成为现实。目前，崔屹和他的同事已经在实验室环境下实现了对前列腺癌、直肠癌等多种癌症的早期诊断。纳米传感器灵敏度很高，在进行血液检测时，当传感器中预置的某种癌细胞抗体遇到相应的抗原时，传感器中的电流会发生变化，通过这种电流变化可以判断血液中癌细胞的种类和浓度。这一研究成果可望于近期发表在美国《科学》杂志上。崔屹指出，目前越来越多的风险投资正在涌入这一领域，但这一技术在实用中还有一些技术难题需要解决。他估计，今后可能会有多种纳米传感器集成在一起被置入人体，以用来早期检测各种疾病。
在半导体芯片领域，如何让芯片体积更小、速度更快是科学界一直研究的课题。目前用于芯片制造的光刻技术已经接近于发展极限，要想把更多的晶体管集成到一块芯片上已经越来越难。目前，美国纳米技术专家们试图把纳米级的半导体材料做成晶体管，从而可以让一块芯片上容纳更多的晶体管。这种芯片的运算速度可望比传统的硅芯片提高上千倍。这一研究方向在取得基础性研究突破后，目前在应用研究中越来越热。据崔屹估计，这一技术可望在10年后达到实用化。
此外，纳米技术在光学材料和生物分子追踪两个领域的应用也是研究热门。在光学材料研究领域，科学家们试图改变某些半导体材料的分子结构，用来生产特定的光学器件。比如，一些科学家试图让某种半导体材料内部具有纳米级的线状结构，这种材料用于显示器制造领域可以大大提高显示器的清晰度和颜色逼真度。而在生物分子追踪领域，科学家把某种纳米颗粒“粘”在生物分子上，然后利用纳米颗粒的发光特性研究生物分子的行踪。这对研究艾滋病病毒等在人体内的活动过程十分有益。
崔屹说，美国在纳米应用研究领域中享有资金和人才优势，一直走在世界前列，但距离纳米技术实用化仍有一段路要走。与美国相比，其他国家则主要处于纳米技术的基础研究阶段。
现年27岁的崔屹毕业于中国科技大学，后在哈佛大学获纳米应用专业博士，目前在加州大学伯克利分校从事研究工作。过去几年，崔屹在《自然》和《科学》等权威杂志上发表多篇研究论文，同时还是美国“米勒”杰出青年科学家奖和20美国材料研究学会金奖得主。
篇5：新托福阅读背景知识精选整合
慢波和快波睡眠
从脑电波“EEG“对睡眠的研究得知，我们每天从入睡到起床的睡眠皆会做梦。睡眠过程中有慢波及快波两种睡眠“参考图一”，入睡开始时先会很快进入慢波睡眠，大约九十分钟後会进入第一次快波睡眠，快波和慢波两者交替发生，一夜的睡眠中约出现三至五次快慢波循环。第一个快波睡眠周期约五分锺长，随後第二个快波睡眠周期按比例渐加长时间。快波睡眠时，睡者有快速眼球转动“REM”的特别现象。快波睡眠时如叫醒睡者，他就知道正在做梦，如果做梦之後过五分锺才叫醒睡者就不会知道自己曾经做过梦。世界各地的睡眠研究报告均证实人在快波睡眠期会做梦，因此快波睡眠又称为“做梦期”。
篇6：新托福阅读背景知识精选整合
睡与梦( dream and sleep)
梦是生活中难解之谜，自古以来引起各种各样的解释和猜想。释梦几乎是精神分析医生及占卜者所独有。笔者就近期对脑电波、香味、音乐与气功的研究科学观点出发，尝试努力把哲学、生理学、心理学及脑科学知识融为一体客观地去探索“睡与梦”的机理，寻找启发性新理论来满足科学及哲学范畴对“睡与梦”解释的需要。透过对“睡与梦”探讨过程，希能使朋友们更好地去认识您自己，发掘自己的潜能。
篇7：新托福阅读背景知识精选整合
脑神经生理学及精神分析学对“梦”的解释
对梦的解释不论古今中外都引起广泛兴趣及争论，大致可分脑神经生理学及精神分析学两学派：
1.脑神经生理学者克里克“F.Crick”是近代代表者。
他认为做事是为了整理记忆，梦并不是提醒我们什麽，而是通过快波睡眠忘记无用讯息，避免储存讯息过度饱和而造成混乱。做事时主要是大脑的脑干部份产生兴奋，发出讯号引起脑视觉区出现影像，前脑把传送到视觉区讯号勉强编成梦，若浪费精力去解释梦意义是毫无价值。
2.精神分析学者佛浴伊德“S.Freud”认为：人有根多欲望和想法被压抑在潜意识深处。入睡後，彼压抑的欲望和观念便会在梦中偷偷进入意识里，但它们是经过化装的，真实意义已经过象征化或符号化。对梦作分析可以了解压抑与问题所在“也可预先参考图二”。
从电脑学发掘“梦”的新理论
快波睡眠等于做梦吗?实验报告证明快波睡眠期约有百分之七十机会做梦。但如果说快波睡眠就是做梦期，在母体内的胎儿及新生儿，快波睡眠高达百分之五十五至百分百。为什麽人生经验几乎是零的胎儿及新生儿，脑中还有什麽压抑欲望或无用讯息须花费那麽多时间去做梦?不论克里克或佛洛伊德的理论都无法获得满意答案。纽曼“Snowman”和伊凡斯“Cleans”两位学者提出从电脑角度去胁助理解人脑做梦机制，他们把人脑入睡後不能感知外界讯息时比拟电脑需暂停正常运作始能输入新程式或修改旧程式，来解释快波睡眠期可能是人脑在膳录或修改程式的时刻。此新启发性理论可满意解释胎儿及新生儿需要那麽长的快波睡眠，因为他们脑中的蛋白质分子正忙著在其脑纹上膳录生存本能及生活所必需的大量程式。此电脑程式观点不仅能把佛洛伊德和克里克理论互相沟通，同时对于析解各种人脑之谜注前迈跨一步。
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