How long has 3-D technology been around? Most of us might think of crowds of teenagers in a 1950's movie house watching Bwana Devil in 3-D. But 3-D technology made its first appearance on the scene in 1838 with the first stereoscope(体视镜). And the first actual 3-D movie was a 1903 film called Le Ariveed'un Train.

    Although it has such a long history, the technology has still remained based on one simple principle—to make 3-D effects you must find a way to project two slightly different pictures to each eye. Modern 3-D technology works by rapidly flickering(闪动)two versions of the movie and projecting them onto each eye. The brain does the rest of the work, combining the two pictures together into one and giving the show the appearance of depth, the third dimension.

    But does this exposure, especially long exposures, cause harm to the child's developing brain and visual system? Unfortunately, long-term studies on new flicker digital 3-D technology and children aren't yet available. We do not know if regular or daily 3-D viewing over years affects the developing visual system, although older 3-D methods basically do the same thing and are not considered harmful.

    The question of possible harm in modern 3-D use in TV is really based on two facts: the amount of time children will now be watching 3-D TV each day and the sensitivity some children show in reaction to 3-D viewing. It is difficult to make actual lab studies of longer term 3-D viewing in children because of the possible harm of the experiment. Researchers will have to wait until 3-D TV technology is already in the marketplace for a number of years, then check heavy 3-D TV watchers and compare them with non-watchers.

    With a 3-D television technology in the home, we will soon be able to answer the question of whether or not longer and more frequent periods of 3-D exposure cause more changes in the visual system. We may find that the bigger problem is the introduction of a new technology that leads to even more time spent on TV rather than playing outdoors.

    North America tours

    Tour North America and discover how the New World became the culturally diverse civilization it is today: the world's greatest melting pot is in your own backyard.

Boston: Colonial History

    Days: 4

    Get your walking shoes ready to follow the footsteps of the American Founding Fathers in Boston. Journey through the landmarks of the American Revolution in this historical city by walking down the Freedom Trail with a Colonial tour guide. Get out of the city with detours to Salem. Lexington, Concord and Plymouth, where you will see where the first shots of the American Revolution were fired.

Civil Rights in the South

    Days: 5

    Journey back to a time of revolution and brotherhood in the heart of the Civil Rights Movement. Follow the path of the marches through Atlanta, Montgomery and Birmingham, as well as the town of Selma, where a peace l protest erupted into what is now called" Bloody Sunday. "Pay respect to the key contributors to civil rights by visiting the Rosa Parks Museum and the home and church of the most famous civil rights activist of them all. Dr Martin Luther King, Jr.

    IL MUNC in Philadelphia

    Days: 4

    The Ivy League Model UN Conference (ILMUNC) is known as a unique educational experience for its focus on international affairs and networking. Students from across the continent will come together to debate and discuss pressing global issues as UN delegates. You can also explore some of downtown Philadelphia's finest attractions including the Philadelphia Museum of Art, the Liberty Bell. Independence Hall before or after the conference.

    Quebec City &Montreal Four Day Spring Tour

    Days: 4

    Montreal and Quebec City are two of the most diverse, beautiful and exciting travel destinations in Canada. Your tour through Quebec's Upper Town includes the beautifully lit National Assembly, Dufferin Terrace, and Chateau Frontenac. Walk along the 17^th-century cobblestone streets of Lower Town, then continue on to Montreal for a visit to Mont Royal, which boasts breathtaking views from the highest point in the cit.

Dear Customers,

    I love slipping into a comfortable chair for a long read－as I relax into the chair; I also relax into the author's words, stories and ideas. The physical book is so elegant that it disappears into the background and what remains is the author's world.

    Today, we, at Amazon, are excited to announce Mindle, a wireless, portable reading device with instant access to more than 90, 000 books, magazines and newspapers.

    We've been working on Mindle for more than three years. Our top design goal was for Mindle to disappear in your hands―to get out of the way－so you can enjoy your reading, also wanted to go beyond the physical book. Mindle is wireless, so whether you're lying in bed or riding a train, you can think of a book and have it in less than 60 seconds. No computer is needed－you do your reading directly from the device.

    We chose the same wireless technology used in advanced mobile phones. But unlike phones there are no monthly wireless bills, no service or data plans, and no yearly contracts. There is no software to install. We want you to get lost in your reading and not in the technology.

    Mindle uses a new kind of display called electronic paper. Sharp and natural with no strong light reading on Mindle is nothing like reading from a computer screen. Mindle weighs only 10.3 ounces－less than a paperback, but can carry two hundred books.

    Enjoy learning about Mindle and many thanks!

    Jeff Bezos Founder CEO

    When we think someone is smart，we say they have a big brain．But are there any facts to prove that statement？

    Yes! In a new study done by Michael McDaniel, a psychologist at Virginia Commonwealth University，bigger does mean smarter. "For all ages and sex groups，"he says，"it is now very clear that intelligence has something to do with brain volume（容量）．"

    McDaniel reached his conclusion after measuring the size and volume of 26 brains with the help of some instruments. He then used standard IQ tests to measure the intelligence of the owners of these brains.

    But do IQ tests really reveal intelligence？McDaniel believes that they do，and here are other studies to backup that point of view．One study last year found that IQ is related to the amount and distribution（分布） of gray matter in the brain．The study showed that the amount of gray matter in certain places was strongly related to high IQ．The distribution of gray matter in the brain，which is different for different people，could explain why one person with a high IQ is good at math but poor at spelling，while someone else with the same IQ has just the opposite ability．

    Yet another recent study found that women have more gray matter（compared with white matter） than men！However，the study also showed that in the areas of the brain specifically（特别地） related to intelligence，men had much more gray matter，which is needed for some tasks，such as doing a math problem. Women, on the other hand, had more white matter, which is necessary for collecting information．And the point is that intelligence can be influenced in different ways．

    "On average，"McDaniel says，"smarter people learn more quickly，make fewer mistakes，and are more productive．"He believes in the use of IQ tests to examine those who want to find a job. So, be well, do good work, and…exercise that brain!

    The days of the hunter are almost over in India. This is partly because there is practically nothing left to kill, and partly because some steps have been taken, mainly by banning tiger-shooting, to protect those animals which still survive.

    Some people say that Man is naturally a hunter. I disagree with this view. Surely our earliest forefathers, who at first possessed no weapons, spent their time digging for roots, and were no doubt themselves often hunted by meat-eating animals.

    I believe the main reason why the modern hunter kills is that he thinks people will admire his courage in overpowering dangerous animals. Of course, there are some who truly believe that the killing is not really the important thing, and that the chief pleasure lies in the joy of the hunt and the beauties of the wild countryside. There are also those for whom hunting in fact offers a chance to prove themselves and risk death by design; these men go out after dangerous animals like tigers, even if they say they only do it to rid the countryside of a threat. I can respect reasons like these, but they are clearly different from the need to strengthen your high opinion of yourself.

    The greatest big-game hunters expressed in their writings something of these finer motives. One of them wrote.

    "You must properly respect what you are after and shoot it cleanly and on the animal's own territory(领地)。You must fix forever in your mind all the wonders of that particular day. This is better than letting him grow a few years older to be attacked and wounded by his own son and eventually eaten, half alive, by other animals, Hunting is not a cruel and senseless killing - not if you respect the thing you kill, not if you kill to enrich your memories, not if you kill to feed your people."

    I can understand such beliefs, and can compare these hunters with those who hunted lions with spears(矛) and bravely caught them by the tail. But this is very different from many tiger-shoots I have seen, in which modern weapons were used. The so-called hunters fired from tall trees or from the backs of trained elephants. Such methods made tigers seem no more dangerous than rabbits.

    Children exposed to "safe" levels of air pollution in the womb(子宫) develop brain damage that damages their concentration, a study has shown.

    The research is the first too link common pollutants such as nitrogen(氮) dioxide and soot(油烟) to changes in the brains of unborn babies that mean they may struggle to focus at school in later life. The findings suggest that even comparatively clean city air could lead to worse academic performance and an increased risk of mental health problems such as addition or attention deficit hyperactivity disorder(缺陷多动障碍).

    In recent years scientists have found that children who grow up surrounded by air pollution are more likely to have a broad range of "neuro(神经)­developmental" difficulties, including autism and various kinds of cognitive(认知) damage. However, only a handful of studies have looked at the ways in which the poisonous gases and microscopic particles(微粒) that mothers and young children take in affect the brain during critical stages of its growth.

    A group led by Monica Guxens, of the Barcelona Institute for Global Health, found that exposure to air pollution before birth appeared to have slowed the development of several brain regions that play an important role in people's capacity for self­denial and sustained effort. This lack of inhibition could in turn cause "cognitive delays" when the children get older, the scientists argue in Biological Psychiatry.

    "We need this function in our daily life," Dr. Guxens said. "It controls our impulses(冲动) and our selective attention. Children need it to learn and for making decisions in later life. We're interested to see what will happen: is there going to be an impact on their academic work, are there going to be clinical implications? It might be that this will lead to problems later."

    The results were drawn from MRI scans of 873 children between the ages of six and ten in Rotterdam. Even though 99.5 percent of their mothers had lived with nanoparticle pollution levels well below EU legal limits while they were pregnant the pollution still appeared to have taken its toll(伤亡人数).

    Children who had been exposed to more pollution in the womb did worse on a test of their ability to block out irrelevant stimuli(刺激). They also had thinner outer layers in the precuneus(楔前叶) and the rostral middle frontal regions of their brains, both of which are involved in cognitive inhibition, which refers to the mind's ability to tune out stimuli that are irrelevant to the task at hand or to the mind's current state.

    Experiments on animals show that so­called fine particles are able to pass through the placenta and affect the brain of the fetus(胎儿). Dr Guxens said there were probably no such thing as a safe concentration of air pollution.