A calorie is a unit of energy, not a measure of weight or nutrient density. The calories you see on nutrition labels，however，are actually kilocalories. The calories on food packaging always refer to kilocalories, even though it just says “calories”. One kilocalorie is the amount of energy required to heat 1 kilogram of water by 1 degree Celsius. Calories in our food all come from one of the three nutrients: fats, carbohydrates and proteins.

In 1990, the U. S. government passed the Nutrition Labeling and Education Act, which means that before any packaged food in the U. S. hits the shelves, food scientists have to measure its nutrients and calories. One way to do this is using a tool called bomb calorimeter（弹氧热卡计）. This tool directly measures the amount of energy that a food contains. To use this tool, scientists place the food in question in a sealed（密封的）container surrounded by water and heat it until the food is completely burned off. Scientists then record the rise in water temperature to determine the number of calories in the product.

Food scientists also rely on a calculation developed by the 19th-century U. S. chemist Wilbur Olin Atwater to indirectly estimate the number of calories in food products. Calorimeters don’t take into account that humans lose some calories through heat and feces（类便）. Atwater’s experiments found that proteins and carbohydrates each have about 4 calories per gram and fats have 9 calories per gram.

However, some experts say that the Atwater system is outdated and inaccurate. A 2012 study found that the energy content of certain foods, such as nuts, could not be accurately calculated by the Atwater system. Besides, it does not take into account the digestive process, but assumes the complete conversion of nutrients to energy.

   Is sleep important to children？A new study says yes.

A new study published this week shows that children who do not get _____ sleep have less control over emotions and are less focused at school.

The National Sleep Foundation _____ 10 to 11 hours of shut-eye per night for children aged between 5 and 12. About 41 million American workers get less than six hours of sleep per night. Now health experts _____ that adults are passing their poor sleeping _____ down to their children.

Reut Gruber is a lead author of the new study. In the study，Gruber and other experts either added or reduced one hour of sleep for _____ children aged 7 to 11. They _____ the children over five nights. The _____ was to see if small changes in the amount of sleep could _____a child's behavior.

“The findings show that for children small changes can make a big _____，and that is why this is meaningful.”

Before the survey began, students were _______to sleep the same amount of hours as they ______ would. Their teachers were asked to ______ the children on thoughtfulness, touchiness and emotional reactions. After five nights of the kids' sleep change, the teachers were asked to take the survey again. ______ their original scores, those who slept one hour less had ______ behavior scores than those who were allowed to sleep an hour more.  Students with less sleep were more annoyed, frustrated and had more problems which need paying ______ to.  The children with more sleep showed ______ in these areas.

“______ less sleep leads to a drop in attention in class, children may ______ on learning and chances to be ______. If they are easily annoyed and frustrated because their bodies and brains are ______, they may not learn as much either,”says Gruber.

   There's a good chance that something you've bought online has been in the hands of a " picker". These are the workers in warehouses (仓库) who pick, pack and ship all those things we ordered.

At Amazon and other companies, they're working side by side with robots. Experts say while the robots are replacing some human workers, the machines aren't quite ready to take over completely.

When a robot finds its storage unit,' it slides underneath, lifts it up and then delivers it to a worker they're called pickers. On a recent day, the computer told a picker to grab what looked like a fantasy board （#t 3#)game. The picker found it, packed it and placed it on the conveyer belt.

"In a traditional fulfillment center where the workers would walk to the different items, it can take hours to fulfill a customer order," Robinson says.

Now, with the help of robots, that task takes minutes and fewer humans.

So is this a sign that we're entering a new industrial revolution?

" It's definitely going to take over a lot of jobs ", says Karen Myers, a scientist at SRI, one of Silicon V alley's oldest research centers.

At the same time, she says, " We're running against the limits of technology. " Take the picker at the Amazon fulfillment center for example. Myers says those skills prove to be uniquely human.

"Our fingers are incredibly flexible and the current generation of robotic operators are getting much, much better," she says. "But they're just not quite there yet."

There's also the robot's brain.

Remember that board game the Amazon worker was looking for? She could barely see the box when it was filled into the storage bin——but she could tell it was a board game. Robots can't do that.

Technologists say that, increasingly, humans will work side by side with robots——instead of robots working alone.

Amazon says robots and humans enabled the Tracy warehouse to fulfill customer orders faster. That means more customers and more human workers.