【每日阅读训练第四期——速度越障13系列】【13-11】科技

2012Michelle

本周二的作业。根据组织的要求，速度练习的内容偏简单，越障的文章么，科技的都是这些框框，挺好玩的。

由于我上周的越障与12-19的重复了，本周我多找了一篇个大家，作为可选的阅读内容，请队友根据自己的时间安排阅读。

Engjoy it!

VOA English

【Time1】
Today, we tell about a woman who can use signals from her brain to move a robotic arm. We tell about efforts to develop an experimental gene treatment for patients with heart disease. And we explain how American computers are helping medical workers in Zimbabwe study the condition of their patients.

A woman paralyzed from the neck down has learned to use her thoughts to control a specially-designed motorized arm. The arm is the product of years of research on mind-controlled artificial limbs.

Researchers in the American state of Pennsylvania say the motorized arm is the most advanced mind-controlled prosthetic, or replacement limb ever made. They created the device to help return some muscle control to Jan Scheuermann. She is suffering from a degenerative neuromuscular disease that paralyzed her from the neck down. She has no control of her arms and legs.

The motorized right arm has a five-fingered, fully-jointed hand. It enables Ms. Scheuermann to pick up and hold objects, and feed herself.

Neurobiologist Andrew Schwartz led the University of Pittsburgh research team that developed the prosthetic arm. He says researchers placed about 200 electrodes in the woman's left cerebral cortex. The left cerebral cortex is the part of the brain that people use to move their right arm.

Dr. Schwartz says the electrodes recorded what the woman's brain cells were doing when she thought about moving the arm.

"And that was enough information that we could then decode from those recordings, what the intention of the subject was, the way she wanted to move her arm and her wrist and close her hand. We could decode the information from those neurons to allow us to do that."
【279】

【Time2】
Jan Scheuermann took part in a 13-week-long program to teach her brain to move the arm. But she did not need that much time. She was able to use her mind to move the robotic arm after just two weeks of training.

She reportedly told researchers that she planned to use the arm to feed herself some chocolate. When she was able to do that, it made the research team very happy.

Andrew Schwartz says his team plans to build another artificial arm, so people like Ms. Scheuermann can hold and move objects using two hands.

"And really the satisfying part is that we're not just making a machine move, we're actually recreating natural humanoid movements. So we're capturing all the beauty and grace and skill of a real movement, and allowing these subjects to basically return to a certain amount of function that they used to have."

The researchers would like to create a wireless system that helps the brain communicate with the robotic limbs. The brain's signals would be changed into messages that computers can understand. People could then use the arms or legs in their homes without wires or help from scientists.

A report describing the prosthetic arm was published in the journal The Lancet.

A patient with an arrhythmia, or irregular heartbeat, might one day be able to have a normal heartbeat with the injection of a single gene. The experimental gene would help to create a natural heart pacemaker. This would end the need for placing an electronic device in a person's chest to control the heartbeat.

Researchers in California created what they are calling "biological pacemaker cells" by adding a single gene to a virus. They then injected the engineered virus into the hearts of guinea pigs. The animals had been bred to suffer from arrhythmia.

The gene caused the creation of an exact copy of the sino-atrial node in the heart's upper right chamber. Other studies have shown that this node helps to keep the heart beating normally. The gene changed heart muscle cells -- called cardiomyocytes -- into natural pacemaker cells.
【349】

【Time3】
Eduardo Marban is director of the Cedars-Sinai Health Institute in Los Angeles. He says the node, called S-A-N, makes up just 10,000 cells among the ten billion heart muscle cells. He says the tissue made by the inserted gene looks almost like the structure it replaces.

"If we were to give scientists who are specialized in this area the data to look at it then compare it to a genuine pacemaker cell -- which, as I said, are exceedingly rare -- to the ones we created by putting a gene into an ordinary heart cell, it'd be, they'd be hard-pressed to tell the difference."

Dr. Marban estimates that five to six billion dollars is spent each year worldwide on electronic pacemakers for millions of patients. But these man-made pacemakers can cause life-threatening infections. And every five to seven years, the batteries that supply power must be changed. This requires another operation.

Dr. Marban says the devices are not right for all patients. And others are too sick to use them. He says researchers plan to put the experimental gene in very sick patients in about two years. They want to prove the gene is both safe and effective.

"Basically, what we are going to look for are patients who already have an electronic pacemaker, who develop a severe infection and need to have the electronic pacemaker taken away. And then, during the time the patients are free of an electronic pacemaker, they, their hearts need to be sustained by some means, and we hope that we would be able to create this biological pacemaker to keep the heart going between treatments."

A report on the natural cardiac pacemaker was published in the journal Nature Biotechnology.

Finally, the United States has launched a program to help improve Zimbabwe's health information management system. The program is meant to strengthen investigation and reporting of disease outbreaks and epidemics.
【315】

【Time4】
You are listening to a group of health workers. They include doctors and medical aides from Manicaland, an area in eastern Zimbabwe. They were happy because America's Centers for Disease Control and Prevention had donated laptop computers and other equipment. The computers will be used to store information about patients they treat in the area.

The donation is part of a $2.1 million gift from PEPFAR -- the President's Emergency Plan for AIDS Relief -- to strengthen Zimbabwe's health management system.

Paula Morgan is the deputy director of the CDC in Zimbabwe.

"Health wise across the board, particularly around disease detection and surveillance, it's important to us to capture all of them, but because we do work with the PEPFAR program, we do concentrate on the HIV and AIDS epidemic."

One of the biggest problems facing Zimbabwe is the HIV/AIDS epidemic. The human immunodeficiency virus, also known as HIV, is the cause of the disease AIDS. The United Nations says new HIV infection rates have dropped by 50 percent in Zimbabwe. But there are still 1.2 million people infected with the virus.

The government in Zimbabwe has little money for health care programs. As a result, the country has failed to meet the targets of what health officials have called the "Abuja Declarations." Under those goals, African governments are required to spend 15 percent of their budgets on health-related issues.
【230】

【Time5】
Ponesai Nyika is a director of the Zimbabwe Ministry of Health.

"This donation is really, really important. It came at a time when we really need it, because what has been happening is at the local clinic they're using hard copies, which is a paper-based system. They record their patients in registers and tally sheets, where they just tally against the patient's age, name and the diagnosis, the treatment that they have been given."

Ponesai Nyika says all of that work is now done with the CDC's donation of computers to Zimbabwe.

PEPFAR is paying a non-profit group, Research Triangle International, to give two weeks of training to health workers in Zimbabwe. Henry Chidawanyika works for the group. He says Zimbabwe needs the help.

"It is very weak in terms of the ability to deliver, mostly because we don't have enough personnel on the ground, we don't have enough equipment, issues of infrastructure, power, connectivity. Health information is a cornerstone of a delivery of a health system, because if you don't know where you are, then you don't know where to go."

Health care workers in Zimbabwe must deal with many diseases and epidemics. A working, dependable health information system will enable them to gather information about groups like pregnant women living with HIV. Medical workers can use that information to help such women receive antiretroviral therapy and treatment for tuberculosis.
【231】

Obstacle
Developing Microbial Cell Factories by Employing Synthetic Small Regulatory RNAs

Biotechnologists have been working hard to address the climate change and limited fossil resource issues through the development of sustainable processes for the production of chemicals, fuels and materials from renewable non-food biomass. One promising sustainable technology is the use of microbial cell factories for the efficient production of desired chemicals and materials.

When microorganisms are isolated from nature, the performance in producing our desired product is rather poor. Metabolic engineering is performed to improve the metabolic and cellular characteristics to achieve enhanced production of desired product at high yield and productivity. Since the performance of microbial cell factory is very important in lowering the overall production cost of the bioprocess, many different strategies and tools have been developed for the metabolic engineering of microorganisms.

One of the big challenges in metabolic engineering is to find the best platform organism and to find those genes to be engineered so as to maximize the production efficiency of the desired chemical. Even Escherichia coli, the most widely utilized simple microorganism, has thousands of genes, the expression of which is highly regulated and interconnected to finely control cellular and metabolic activities. Thus, the complexity of cellular genetic interactions is beyond our intuition and thus it is very difficult to find effective target genes to engineer. Together with gene amplification strategy, gene knockout strategy has been an essential tool in metabolic engineering to redirect the pathway fluxes toward our desired product formation.

However, experiment to engineer many genes can be rather difficult due to the time and effort required; for example, gene deletion experiment can take a few weeks depending on the microorganisms. Furthermore, as certain genes are essential or play important roles for the survival of a microorganism, gene knockout experiments cannot be performed. Even worse, there are many different microbial strains one can employ. There are more than 50 different E. coli strains that metabolic engineer can consider to use. Since gene knockout experiment is hard-coded (that is, one should repeat the gene knockout experiments for each strain), the result cannot be easily transferred from one strain to another.

A paper published in Nature Biotechnology online January 20 addresses this issue and suggests a new strategy for identifying gene targets to be knocked out or knocked down through the use of synthetic small RNA. A Korean research team led by Distinguished Professor Sang Yup Lee at the Department of Chemical and Biomolecular Engineering, Korea Advanced Institute of Science and Technology (KAIST), reported that synthetic small RNA can be employed for finely controlling the expression levels of multiple genes at the translation level. Already well-known for their systems metabolic engineering strategies, Professor Lee's team added one more strategy to efficiently develop microbial cell factories for the production of chemicals and materials.

Gene expression works like this: the hard-coded blueprint (DNA) is transcribed into messenger RNA (mRNA), and the coding information in mRNA is read to produce protein by ribosomes. Conventional genetic engineering approaches have often targeted modification of the blueprint itself (DNA) to alter organism's physiological characteristics. Again, engineering the blueprint itself takes much time and effort, and in addition, the results obtained cannot be transferred to another organism without repeating the whole set of experiments. This is why Professor Lee and his colleagues aimed at controlling the gene expression level at the translation stage through the use of synthetic small RNA. They created novel RNAs that can regulate the translation of multiple messenger RNAs (mRNA), and consequently varying the expression levels of multiple genes at the same time. Briefly, synthetic regulatory RNAs interrupt gene expression process from DNA to protein by destroying the messenger RNAs to different yet controllable extents. The advantages of taking this strategy of employing synthetic small regulatory RNAs include simple, easy and high-throughput identification of gene knockout or knockdown targets, fine control of gene expression levels, transferability to many different host strains, and possibility of identifying those gene targets that are essential.

As proof-of-concept demonstration of the usefulness of this strategy, Professor Lee and his colleagues applied it to develop engineered E. coli strains capable of producing an aromatic amino acid tyrosine, which is used for stress symptom relief, food supplements, and precursor for many drugs. They examined a large number of genes in multiple E. coli strains, and developed a highly efficient tyrosine producer. Also, they were able to show that this strategy can be employed to an already metabolically engineered E. coli strain for further improvement by demonstrating the development of highly efficient producer of cadaverine, an important platform chemical for nylon in the chemical industry.

This new strategy, being simple yet very powerful for systems metabolic engineering, is thus expected to facilitate the efficient development of microbial cell factories capable of producing chemicals, fuels and materials from renewable biomass.

【794】

选读
Obstacle2

'Quadruple Helix' DNA Discovered in Human Cells

In 1953, Cambridge researchers Watson and Crick published a paper describing the interweaving 'double helix' DNA structure -- the chemical code for all life.

Now, in the year of that scientific landmark's 60th Anniversary, Cambridge researchers have published a paper proving that four-stranded 'quadruple helix' DNA structures -- known as G-quadruplexes -- also exist within the human genome. They form in regions of DNA that are rich in the building block guanine, usually abbreviated to 'G'.

The findings mark the culmination of over 10 years investigation by scientists to show these complex structures in vivo -- in living human cells -- working from the hypothetical, through computational modelling to synthetic lab experiments and finally the identification in human cancer cells using fluorescent biomarkers.

The research, published January 20 in Nature Chemistry and funded by Cancer Research UK, goes on to show clear links between concentrations of four-stranded quadruplexes and the process of DNA replication, which is pivotal to cell division and production.

By targeting quadruplexes with synthetic molecules that trap and contain these DNA structures -- preventing cells from replicating their DNA and consequently blocking cell division -- scientists believe it may be possible to halt the runaway cell proliferation at the root of cancer.

"We are seeing links between trapping the quadruplexes with molecules and the ability to stop cells dividing, which is hugely exciting," said Professor Shankar Balasubramanian from the University of Cambridge's Department of Chemistry and Cambridge Research Institute, whose group produced the research.

"The research indicates that quadruplexes are more likely to occur in genes of cells that are rapidly dividing, such as cancer cells. For us, it strongly supports a new paradigm to be investigated -- using these four-stranded structures as targets for personalised treatments in the future."

Physical studies over the last couple of decades had shown that quadruplex DNA can form in vitro -- in the 'test tube', but the structure was considered to be a curiosity rather than a feature found in nature. The researchers now know for the first time that they actually form in the DNA of human cells.

"This research further highlights the potential for exploiting these unusual DNA structures to beat cancer -- the next part of this pipeline is to figure out how to target them in tumour cells," said Dr Julie Sharp, senior science information manager at Cancer Research UK.

"It's been sixty years since its structure was solved but work like this shows us that the story of DNA continues to twist and turn."

The study published January 20 was led by Giulia Biffi, a researcher in Balasubramaninan's lab at the Cambridge Research Institute.

By building on previous research, Biffi was able to generate antibody proteins that detect and bind to areas in a human genome rich in quadruplex-structured DNA, proving their existence in living human cells.

Using fluorescence to mark the antibodies, the researchers could then identify 'hot spots' for the occurrence of four-stranded DNA -- both where in the genome and, critically, at what stage of cell division.

While quadruplex DNA is found fairly consistently throughout the genome of human cells and their division cycles, a marked increase was shown when the fluorescent staining grew more intense during the 's-phase' -- the point in a cell cycle where DNA replicates before the cell divides.

Cancers are usually driven by genes called oncogenes that have mutated to increase DNA replication -- causing cell proliferation to spiral out of control, and leading to tumour growth.

The increased DNA replication rate in oncogenes leads to an intensity in the quadruplex structures. This means that potentially damaging cellular activity can be targeted with synthetic molecules or other forms of treatments.

"We have found that by trapping the quadruplex DNA with synthetic molecules we can sequester and stabilise them, providing important insights into how we might grind cell division to a halt," said Balasubramanian.

"There is a lot we don't know yet. One thought is that these quadruplex structures might be a bit of a nuisance during DNA replication -- like knots or tangles that form.

"Did they evolve for a function? It's a philosophical question as to whether they are there by design or not -- but they exist and nature has to deal with them. Maybe by targeting them we are contributing to the disruption they cause."

The study showed that if an inhibitor is used to block DNA replication, quadruplex levels go down -- proving the idea that DNA is dynamic, with structures constantly being formed and unformed.

The researchers also previously found that an overactive gene with higher levels of Quadruplex DNA is more vulnerable to external interference.

"The data supports the idea that certain cancer genes can be usefully interfered with by small molecules designed to bind specific DNA sequences," said Balasubramanian.

"Many current cancer treatments attack DNA, but it's not clear what the rules are. We don't even know where in the genome some of them react -- it can be a scattergun approach.

"The possibility that particular cancer cells harbouring genes with these motifs can now be targeted, and appear to be more vulnerable to interference than normal cells, is a thrilling prospect.

"The 'quadruple helix' DNA structure may well be the key to new ways of selectively inhibiting the proliferation of cancer cells. The confirmation of its existence in human cells is a real landmark."

【895】

铁板神猴

顶楼微笑~~ 大米姐你帮我督促督促映雪 ==周日我提醒过她了还是忘了……

辣子安

明儿起来再补9,10,11
先占个板凳

1:32
1:38
1:40
1:09
1:09
4:15. 生物的竟然会读得很有劲=。=...这是神马情况=。=

attractg

快速占位~~！！！大米姐辛苦~~

映雪瑶渊

= =我周日还记得。。做事起来就忘了。。o(╯□╰)o
占楼顶米爷。发帖不好发啊。。找内容难啊

IrisZZZ

2'09'
the artificial limb is made to help a woman who is paralized from neck down to control her right arm

2‘19’
the artificial can show humanoid movement.
One kind of gene was made to help the heart beats normally by injection into the body

2’30‘
the gene is suposed to be efficient,but yet not tested on humans

1’45‘
一个医务中心收到了很多捐款
用于控制AIDS 这个地方的艾滋病新发率比以前好多了 但是财政预算没有达到目标

1’43‘
The donation comes right the time it is needed
the nurses used to paper copy the imformation about the patients
now computers can help then gather imformation

7'13'
障碍对我来说真的很障碍。。。

kudoucliff

（1）1:32，The passage introduced the use of an artificial arm made up by a researcher and described how it was in use. People can control the artificial arm just by using the brain, the left one connecting with the right arm. This artificial arm provides a possibility for doctors to heal some people who lost the arms.
（2）1:53，The passage introduced a woman who succeeded in learning how to use the artificial arm. Researchers planned to find a method that can help brain communicate with the artificial arms without wire; in this way, we can heal many diseases.
（3）1:43，The passage described both the advantages and disadvantages of the artificial pacemaker, which was placed to the muscle tissue of the heart. Hopefully, it may be applied to very sick people. A report of the pacemaker has been published, claiming that this invention has brought benefits to country Z people.
（4）1:12，The passage introduced that USA institution donated PCs to Z country, making doctors there very delight, because these computers can be used to improve health management. Local people suffer from HIV epidemic, which is the major cause of AIDS. Although the portion of people got AIDS has been dropped, there are still many people suffering from it.
（5）1:07，In the passage, the receiver of country Z expressed highly appreciation to the donation, because it really meets the needs. It is expected that many diseases can be controlled under the use of new computers, which can help detect and record diseases.
（6）5:39，The passage introduced that the microbiology played an important role in producing micro-products, using the microbes. However, the challenges are very obvious. They have to use genetic amplification as well as genetic deletion to select what is useful and give up what is useless. A group of scientists claimed that they have developed methods-using mRNA-to accomplish the selection process without damaging the DNA and that they have succeeded in producing one food supplement.

修一一

1‘45   how a women can control robotic arm through her brain.
1'58   走神了，再读一遍。。。 2’14  scientists would creat another arm; they would inject gene to therapy some diseases
1'55  the insufficient of the therapy
1'37  the donation makes the treat better
1'09  貌似主题跟上一个一样
越障：头晕了今天。。。

fifiwong

1.(01'52'')a woman can use signals from the brain to control a robotic arm,which helps her do some daily work,introduce some characteristics of the arm and how it works
2.(02'17'')researchers aim at reacting humanoid movements, they are trying to make a wireless system that helps the brain communicate with the robotic limbs, it is quite convenient to users. a patient with irregular heartbeat, the pacemaker would help
3.(01'47'')for some very sick patients,the pacemaker may cause serious infections, Dr.M points out that the device is not right for all patients.
4.(01'44'')the american health center has donated computers and other equipment to Z, it's important to detect and capture deseases, but the aids is the biggest problem in Z, many people are infected with the virus and the government has to spend a big proportion of the budget to deal with this problem
5. (01'44'')the donation is really important because it helps health workers to record patients' information
obstacle(03'56'')
main idea: microbial cell factories
structure: introduce microbial cell factories and its performance,two challenges, suggest a new strategy,how gene expression works, give some proof to support the strategy, and the expectation.

2012Michelle

一早爬过来给大家再发一段补充的阅读材料，昨晚半夜听了奥巴马第二任期就职演讲，很不错。
视频：
http://v.youku.com/v_show/id_XNTA1MTIyNDYw.html

文稿：
Inaugural Address
（From Whitehoue website)

By President Barack Hussein Obama

My fellow citizens: I stand here today humbled by the task before us, grateful for the trust you've bestowed, mindful of the sacrifices borne by our ancestors.

I thank President Bush for his service to our nation -- (applause) -- as well as the generosity and cooperation he has shown throughout this transition.

Forty-four Americans have now taken the presidential oath. The words have been spoken during rising tides of prosperity and the still waters of peace. Yet, every so often, the oath is taken amidst gathering clouds and raging storms. At these moments, America has carried on not simply because of the skill or vision of those in high office, but because we, the people, have remained faithful to the ideals of our forebears and true to our founding documents.

So it has been; so it must be with this generation of Americans.

That we are in the midst of crisis is now well understood. Our nation is at war against a far-reaching network of violence and hatred. Our economy is badly weakened, a consequence of greed and irresponsibility on the part of some, but also our collective failure to make hard choices and prepare the nation for a new age. Homes have been lost, jobs shed, businesses shuttered. Our health care is too costly, our schools fail too many -- and each day brings further evidence that the ways we use energy strengthen our adversaries and threaten our planet.

These are the indicators of crisis, subject to data and statistics. Less measurable, but no less profound, is a sapping of confidence across our land; a nagging fear that America's decline is inevitable, that the next generation must lower its sights.

Today I say to you that the challenges we face are real. They are serious and they are many. They will not be met easily or in a short span of time. But know this America: They will be met. (Applause.)

On this day, we gather because we have chosen hope over fear, unity of purpose over conflict and discord. On this day, we come to proclaim an end to the petty grievances and false promises, the recriminations and worn-out dogmas that for far too long have strangled our politics. We remain a young nation. But in the words of Scripture, the time has come to set aside childish things. The time has come to reaffirm our enduring spirit; to choose our better history; to carry forward that precious gift, that noble idea passed on from generation to generation: the God-given promise that all are equal, all are free, and all deserve a chance to pursue their full measure of happiness. (Applause.)

In reaffirming the greatness of our nation we understand that greatness is never a given. It must be earned. Our journey has never been one of short-cuts or settling for less. It has not been the path for the faint-hearted, for those that prefer leisure over work, or seek only the pleasures of riches and fame. Rather, it has been the risk-takers, the doers, the makers of things -- some celebrated, but more often men and women obscure in their labor -- who have carried us up the long rugged path towards prosperity and freedom.

For us, they packed up their few worldly possessions and traveled across oceans in search of a new life. For us, they toiled in sweatshops, and settled the West, endured the lash of the whip, and plowed the hard earth. For us, they fought and died in places like Concord and Gettysburg, Normandy and Khe Sahn.

Time and again these men and women struggled and sacrificed and worked till their hands were raw so that we might live a better life. They saw America as bigger than the sum of our individual ambitions, greater than all the differences of birth or wealth or faction.

This is the journey we continue today. We remain the most prosperous, powerful nation on Earth. Our workers are no less productive than when this crisis began. Our minds are no less inventive, our goods and services no less needed than they were last week, or last month, or last year. Our capacity remains undiminished. But our time of standing pat, of protecting narrow interests and putting off unpleasant decisions -- that time has surely passed. Starting today, we must pick ourselves up, dust ourselves off, and begin again the work of remaking America. (Applause.)

For everywhere we look, there is work to be done. The state of our economy calls for action, bold and swift. And we will act, not only to create new jobs, but to lay a new foundation for growth. We will build the roads and bridges, the electric grids and digital lines that feed our commerce and bind us together. We'll restore science to its rightful place, and wield technology's wonders to raise health care's quality and lower its cost. We will harness the sun and the winds and the soil to fuel our cars and run our factories. And we will transform our schools and colleges and universities to meet the demands of a new age. All this we can do. All this we will do.

Now, there are some who question the scale of our ambitions, who suggest that our system cannot tolerate too many big plans. Their memories are short, for they have forgotten what this country has already done, what free men and women can achieve when imagination is joined to common purpose, and necessity to courage. What the cynics fail to understand is that the ground has shifted beneath them, that the stale political arguments that have consumed us for so long no longer apply.
The question we ask today is not whether our government is too big or too small, but whether it works -- whether it helps families find jobs at a decent wage, care they can afford, a retirement that is dignified. Where the answer is yes, we intend to move forward. Where the answer is no, programs will end. And those of us who manage the public's dollars will be held to account, to spend wisely, reform bad habits, and do our business in the light of day, because only then can we restore the vital trust between a people and their government.

Nor is the question before us whether the market is a force for good or ill. Its power to generate wealth and expand freedom is unmatched. But this crisis has reminded us that without a watchful eye, the market can spin out of control. The nation cannot prosper long when it favors only the prosperous. The success of our economy has always depended not just on the size of our gross domestic product, but on the reach of our prosperity, on the ability to extend opportunity to every willing heart -- not out of charity, but because it is the surest route to our common good. (Applause.)

As for our common defense, we reject as false the choice between our safety and our ideals. Our Founding Fathers -- (applause) -- our Founding Fathers, faced with perils that we can scarcely imagine, drafted a charter to assure the rule of law and the rights of man -- a charter expanded by the blood of generations. Those ideals still light the world, and we will not give them up for expedience sake. (Applause.)

And so, to all the other peoples and governments who are watching today, from the grandest capitals to the small village where my father was born, know that America is a friend of each nation, and every man, woman and child who seeks a future of peace and dignity. And we are ready to lead once more. (Applause.)

Recall that earlier generations faced down fascism and communism not just with missiles and tanks, but with the sturdy alliances and enduring convictions. They understood that our power alone cannot protect us, nor does it entitle us to do as we please. Instead they knew that our power grows through its prudent use; our security emanates from the justness of our cause, the force of our example, the tempering qualities of humility and restraint.

We are the keepers of this legacy. Guided by these principles once more we can meet those new threats that demand even greater effort, even greater cooperation and understanding between nations. We will begin to responsibly leave Iraq to its people and forge a hard-earned peace in Afghanistan. With old friends and former foes, we'll work tirelessly to lessen the nuclear threat, and roll back the specter of a warming planet.

We will not apologize for our way of life, nor will we waver in its defense. And for those who seek to advance their aims by inducing terror and slaughtering innocents, we say to you now that our spirit is stronger and cannot be broken -- you cannot outlast us, and we will defeat you. (Applause.)

For we know that our patchwork heritage is a strength, not a weakness. We are a nation of Christians and Muslims, Jews and Hindus, and non-believers. We are shaped by every language and culture, drawn from every end of this Earth; and because we have tasted the bitter swill of civil war and segregation, and emerged from that dark chapter stronger and more united, we cannot help but believe that the old hatreds shall someday pass; that the lines of tribe shall soon dissolve; that as the world grows smaller, our common humanity shall reveal itself; and that America must play its role in ushering in a new era of peace.

To the Muslim world, we seek a new way forward, based on mutual interest and mutual respect. To those leaders around the globe who seek to sow conflict, or blame their society's ills on the West, know that your people will judge you on what you can build, not what you destroy. (Applause.)

To those who cling to power through corruption and deceit and the silencing of dissent, know that you are on the wrong side of history, but that we will extend a hand if you are willing to unclench your fist. (Applause.)

To the people of poor nations, we pledge to work alongside you to make your farms flourish and let clean waters flow; to nourish starved bodies and feed hungry minds. And to those nations like ours that enjoy relative plenty, we say we can no longer afford indifference to the suffering outside our borders, nor can we consume the world's resources without regard to effect. For the world has changed, and we must change with it.

As we consider the role that unfolds before us, we remember with humble gratitude those brave Americans who at this very hour patrol far-off deserts and distant mountains. They have something to tell us, just as the fallen heroes who lie in Arlington whisper through the ages.

We honor them not only because they are the guardians of our liberty, but because they embody the spirit of service -- a willingness to find meaning in something greater than themselves.

And yet at this moment, a moment that will define a generation, it is precisely this spirit that must inhabit us all. For as much as government can do, and must do, it is ultimately the faith and determination of the American people upon which this nation relies. It is the kindness to take in a stranger when the levees break, the selflessness of workers who would rather cut their hours than see a friend lose their job which sees us through our darkest hours. It is the firefighter's courage to storm a stairway filled with smoke, but also a parent's willingness to nurture a child that finally decides our fate.

Our challenges may be new. The instruments with which we meet them may be new. But those values upon which our success depends -- honesty and hard work, courage and fair play, tolerance and curiosity, loyalty and patriotism -- these things are old. These things are true. They have been the quiet force of progress throughout our history.

What is demanded, then, is a return to these truths. What is required of us now is a new era of responsibility -- a recognition on the part of every American that we have duties to ourselves, our nation and the world; duties that we do not grudgingly accept, but rather seize gladly, firm in the knowledge that there is nothing so satisfying to the spirit, so defining of our character than giving our all to a difficult task.

This is the price and the promise of citizenship. This is the source of our confidence -- the knowledge that God calls on us to shape an uncertain destiny. This is the meaning of our liberty and our creed, why men and women and children of every race and every faith can join in celebration across this magnificent mall; and why a man whose father less than 60 years ago might not have been served in a local restaurant can now stand before you to take a most sacred oath. (Applause.)

So let us mark this day with remembrance of who we are and how far we have traveled. In the year of America's birth, in the coldest of months, a small band of patriots huddled by dying campfires on the shores of an icy river. The capital was abandoned. The enemy was advancing. The snow was stained with blood. At the moment when the outcome of our revolution was most in doubt, the father of our nation ordered these words to be read to the people:

"Let it be told to the future world...that in the depth of winter, when nothing but hope and virtue could survive... that the city and the country, alarmed at one common danger, came forth to meet [it]."

America: In the face of our common dangers, in this winter of our hardship, let us remember these timeless words. With hope and virtue, let us brave once more the icy currents, and endure what storms may come. Let it be said by our children's children that when we were tested we refused to let this journey end, that we did not turn back nor did we falter; and with eyes fixed on the horizon and God's grace upon us, we carried forth that great gift of freedom and delivered it safely to future generations.

Thank you. God bless you. And God bless the United States of America. (Applause.)