In colleges around the country, most students are also workers.

    The reality of college can be pretty different from the images presented in movies and television. Instead of the students who wake up late, party all the time, and study only before exams, many colleges are full of students with pressing schedules of not just classes and activities, but real jobs, too.

This isn't a temporary phenomenon. The share of working students has been on the rise since the 1970s, and one-fifth of students work all year round. About one-quarter of those who work while attending school have both a full-course load and a full-time job. The arrangement can help pay for tuition (学费) and living costs, obviously. And there's value in it beyond the direct cause: such jobs can also be critical for developing important professional and social skills that make it easier to land a job after graduation. With many employers looking for students with already-developed skill sets, on-the-job training while in college can be the best way to ensure a job later on.

But it's not all upside. Even full-time work may not completely cover the cost of tuition and living expenses. The study notes that if a student worked a full-time job at the federal minimum wage, they would earn just over $15,000 each year, certainly not enough to pay for tuition, room, and board at many colleges without some serious financial aid. That means that though they're sacrificing time away from the classroom, many working students will still graduate with at least some debt. And working full time can reduce the chance that students will graduate at all, by cutting into the time available for studying and attending classes.

There is little reward for attending but not finishing college. Students who wind up leaving school because of difficulty in managing work and class are likely to find themselves stuck in some of the same jobs they might have gotten if they hadn't gone at all. The difficulty of working too much while in school can create a cycle that pushes students further into debt without receiving any of the financial or career benefits.

    Have your parents ever inspected your room to see if you cleaned it properly? Imagine having your entire houses, garage, and yard inspected at any time -- with no warning. Inspections were a regular part of lighthouse (灯塔) living, and a keeper's reputation depended on results. A few times each year, an inspector arrived to look over the entire light station. The inspections were supposed to be a surprise, but keeper sometimes had advance notice.

    Once lighthouses had telephones, keepers would call each other to warn that the inspector was approaching. After boats began flying special flags noting the inspector aboard, the keeper's family made it a game to see who could notice the boat first. As soon as someone spotted the boat, everyone would do last-minute tidying and change into fancy clothes. The keeper then scurried to put on his dress uniform and cap. Children of keepers remember inspectors wearing white gloves to run their fingers over door frames and windowsills looking for dust.

    Despite the serious nature of inspections, they resulted in some funny moments. Betty Byrnes remembered when her mother did not have time to wash all the dishes before an inspection. At the time, people did not have dishwashers in their homes. In an effort to clean up quickly, Mrs. Byrnes tossed all the dishes into a big bread pan, covered them with a cloth and stuck them in the oven. If the inspector opened the oven door, it would look like bread was baking. he never did.

    One day, Glenn Furst's mother put oil on the kitchen floor just before the inspector entered their house. Like floor wax, the oil made the floors shiny and helped protect the wood. This time, though, she used a little too much oil. When the inspector extended his hand to greet Glenn's mother, he slipped on the freshly oiled surface. "He came across that floor waving his arms like a young bird attempting its first flight," Glenn late wrote. After he steadied himself, he shook Glenn's mother's hand, and the inspection continued as though nothing had happened.

    Dry Ice is a unique substance which has many uses. Essentially, dry ice is frozen CO2. The first report of what we now call dry ice came from the French chemist Charles Thilorier in 1834. In 1924, the Drylee Corporation of America named the solid form of CO2 as "Dry Ice", which is what it is popularly called today.

    At normal atmospheric pressure, CO2changes directly from solid to gas. It skips the liquid phase（阶段）which makes regular ice wet. Frozen CO2is also much colder than regular ice. But regular ice freezes at 32 degrees Fahrenheit, CO2 changes from gas to solid at -109.3 degrees Fahrenheit. This extremely cold temperature makes it very dangerous to handle with bare hands. It can cause frostbite in a very short period of time.

    Dry ice has been used for a variety of purposes throughout the past century. Its primary use is to refrigerate food when electrical refrigeration isn't available. Through the process of sublimation (when CO2 changes from solid to gas), it can maintain cold food for a long time.

    If you've ever been to a play and seen heavy fog on the ground, it is likely that you have seen dry ice in action. This effect can be achieved because CO2 is heavier than air, so evaporated （挥发的）CO2 will sink and accumulate on the ground.

    Another interesting use for this substance is to bait（诱杀）insects like mosquitoes. These insects have sensors which guide them to CO2. They find the high concentration of CO2 in dry ice quite attractive.

    Mars has long been a mystery for human beings. We have been looking for evidence of life on Mars. In the 1960s scientists guessed that the polar ice cap of Mars was made of frozen CO2. More recent observations have shown that while the topmost layer consists of frozen CO2, the most of it is probably regular frozen water.

    In 1869, the Smiley family purchased an area of land about 100 miles north of New York City. Over time, some of their property and much of the surrounding landscape became the Mohonk Preserve, which has since grown to 8,000 acres and attracts visitors and rock climbers.

    But the Mohonk Preserve also has a long scientific legacy. In the 1930s, Dan Smiley, a descendent of the original owners, began keeping track of the plants and animals that lived in the area.

    Megan Napoli is a research ecologist with the Mohonk Preserve in New York. She thinks Smiley's efforts produced a rare long-term data set of observations, which is useful for studying the impacts of climate change. For instance, other research has shown that songbirds are migrating north earlier and earlier in the spring.

    It's important for the birds to arrive at the proper time in the spring, because they need to time their arrival with the insect emergence. So they need to be here to establish their nesting sites, lay their eggs. Once the eggs hatch, they have their baby birds, so they need to time it when the insects are most abundant.

    Napoli has begun analyzing about 76,000 observations of songbird migration dates collected by Smiley and his team to see if they, too, show that climate change has altered the timing of migrations. Her results suggest that they do.

    Napoli found that short-distance migrants that spend their winters in the southern U. S. now arrive an average of eleven days earlier than they did in the 1930s. Long-distance migrants that overwinter in the tropics arrive roughly a week earlier. Napoli presented her results at a recent Ecological Society of America meeting in Portland, Oregon.

    Meanwhile, who knows how many other long-term, personal data collections like Smiley's are out there, waiting to be discovered and to help improve official attempts to track the planet's changes.

    We work with Cambridge County Council's Participation Team to create opportunities for young people to visit the University and learn more about it. The following events are scheduled for the 2019/2020 academic year.

    Superstar workshops

    12 engaging workshops are planned for young people aged 7 to 11. These half-day visits will be held throughout the year, at times when young people are not at school. If participants complete 8 of the 12 workshops, they will be awarded the nationally recognized Superstar Crest Award.

Please note, workshops will only run if we have a sufficient number of attendees (usually around 3+ participants).

    Explore University Days

    Explore University Days are for young people aged 12-15. Participants visit the University for two days and engage with a range of university-related workshops, and other fun activities.

Previous participants have engaged with the following:

    Visited the Sports Centre

    Took part in a Neuroscience workshop

    Enjoyed a two-course meal at a University College

    Dates will be confirmed in early December 2019, and a schedule for event will follow in the New Year.

    Events for post-16 students

    If you are studying for your post-16 qualifications and are considering applying for Cambridge or would like to find out more about a specific subject, the following events might be for you:

    University and College Open Days

    Subject Master classes

    Cambridge Science Festival

The Mona Lisa is the famous Leonardo da Vinci painting of a woman with a mysterious smile. This week, the painting gave up a secret.

Scientists used X-rays to examine the chemical organization of an extremely small part of the more than 500-year-old painting. The researchers discovered a technique Leonardo used in the work. A team in France and Britain discovered an oil paint used for the Mona Lisa was a special, new chemical mixture. It suggests that the Italian artist may have been in an experimental mood when he set to work on the painting early in the 16th century.

"He was someone who loved to experiment, and each of his paintings is completely different technically," said Victor Gonzalez. He is the study's lead writer. "In this case, it's interesting to see that indeed there is a specific technique for the ground layer of the Mona Lisa," he said in an interview with The Associated Press. Specifically, the researchers found a rare compound, plumbonacrite (水蛭石), in Leonardo's first layer of paint. The discovery, Gonzalez said, proved that da Vinci most likely used lead oxide to thicken and help dry his paint.

The scientists looked into its atomic structure using X-rays in a synchrotron (同步加速器). The machine moves particles at close to the speed of light, permitting researchers to look deeper into the paint structure. "Plumbonacrite is really a fingerprint of his recipe," Gonzalez said. "It's the first time we can actually chemically prove it."

Dutch artist Rembrandt may have used a similar mixture when he was painting in the 17th century. Gonzalez and other researchers have found plumbonacrite in his work, too. "It also tells us that those recipes were passed on for centuries," Gonzalez said. "It was a very good recipe."

But the Mona Lisa and additional works by Leonardo still have other secrets to tell. "There are plenty, plenty more things to discover," Gonzalez said. "What we are saying is just a little brick more in the knowledge."