New York Time—A gunman killed eight people at a mall in Omaha this afternoon and then killed himself, setting off panic among holiday shoppers, the police said.

    "The person who we believe to be the shooter has died from self-inflicted gunshot wounds," Sergeant Teresa Negron of the Omaha Police Department said at televised news." We have been able to clear the mall," she said." We don't believe we have any other shooters." The police said that at least five other people had been injured in the shootings.

    She did not give the shooter's identity." We are still conducting the investigation," Sergeant Negron said, adding that the city's mayor, who was out of town, was on his way back to Omaha.

    She said the police received a 911 call from someone inside the Westroads Mall on the west side of Omaha, and shots could be heard in the background. The first police officers arrived at the mall six minutes after the first call, she said but by then the shootings were over.

    It is reported that the gunman left a suicide note that was found at his home by relatives. A law enforcement official who spoke on condition of anonymity（匿名）said the note indicated that the gunman wanted to "go out in style."

    The shootings broke the usually ordinary routine of holiday shopping. The gunman was said by some witnesses to have fired about 20 shots into a crowd. Some customers and workers ran screaming from the mall, while others dived into dressing rooms to hide from the shooter.

    Shoppers and store workers were trapped inside the mall, which has roughly 135 stores. Others streamed out of mall exits with their hands raised. President Bush was in Omaha this morning to deliver a speech, but he had left the city by the time the shootings took place.

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    If you are human, you can't help but experience times when everything seems to be going wrong and you feel as if your life is completely out of control. It is during those “down times” that words of encouragement from family, friends, co-workers or even strangers can lighten your spirits. It is also during those times that destructive(有害的) words can sink you deeper and deeper into depression(沮丧).

    For example, consider this story about a group of frogs who were traveling through the woods when two of them fell into a deep pit（坑）. All of the other frogs gathered around the pit. When they saw how deep the pit was, they told the two unfortunate frogs they would never get out.

    The two frogs ignored the comments and tried to jump out of the pit. The other frogs kept telling them to stop. Finally, one of the frogs took heed of what the other frogs were saying and simply gave up. He fell down and died. The other frog continued to jump as hard as he could. Once again the crowd of frogs shouted at him to stop the pain. The more they shouted, the harder he jumped and finally he made it to safety.

    When he got out, the other frogs asked him why he continued to jump when they were all shouting at him to simply quit. The frog explained to them that he was a little bit deaf. He thought they were encouraging him the entire time.

    Every time you have a chance to say either something positive or negative to another human being, do choose the chance to say something positive! Don't let those opportunities get away from you. Your words have a large amount of power. Use them wisely. You really never know just how much they can mean to someone else.

    A couple near Pittsburgh finally removed an alarm clock from inside their walls. It had been stuck there for more than ten years.

    Every night between 6:50 and 7:50, the alarm clock stuck in the living room wall rang. Sylvia and Jerry Lynn heard the alarm ring at the same time every evening for 13 years. And they finally had the clock removed after their story gained national attention.

    Keith Andreen and Dawn Michelucci work for Low-Cost Heating and Air Conditioning. They came to get the clock out of the wall through the couple's garage.

    “This is the first time that I had to remove a clock from inside a wall,” Andreen told CBS Pittsburgh.

    Jerry accidentally dropped the clock down an air vent (通风口) while making home repairs in 2004. The couple expected the clock to die after a few months. However, its battery remained undamaged even as it was pulled from the wall. Jerry said they finally got used to the nightly alarm and even considered it “kind of cute”. So he chose to leave it in the wall as a conversation starter. “You're sitting around playing cards and it goes off,” he told Inside Edition. “Is that an alarm clock? Why is the alarm clock going off? It's in the wall.”

    After 13 years, Jerry said the clock looked almost exactly how he remembered it when he dropped it in the wall. “It is a travel alarm clock,” he said. The couple plans to keep their nightly routine going by placing the clock in their room and keeping the alarm set for 7:50 p.m.

    American high school students are terrible writers, and one education reform group thinks it has an answer: robots. Or, more accurately, robot-readers—computers programmed to scan students' essays and spit out a grade.

    Mark Shermis, professor of the College of Education at the University of Akron, is helping to hold a contest, set up by the William and Flora Hewlett Foundation (WFHF), which promises $ 100,000 in prize money to programmers who write the best automated grading software. "If you're a high school teacher and you give a writing task, you're walking home with 150 essays," Shermis said. "You're going to need some help."

    Automated essay grading was first proposed in the 1960s, but computers back then were not up to the task. In the late 1990s, as technology improved, several textbooks and testing companies jumped into the field. Today, computers are used to grade essays on South Dakota's student writing assessments and a handful of other exams, including the TOEFL test of English fluency, taken by foreign students.

    The Hewlett contest aims to show that computers can grade as well as English teachers—only much more quickly and without all that depressing red ink. "Automated essay scoring is objective," Shermis said. "And it can be done immediately. If students finish an essay at 10 pm, they will get a result at 10: 01 pm."

    Take, for instance, the Intelligent Essay Assessor, a web-based tool marketed by Pearson Education, Inc. Within seconds, it can analyze an essay for spelling, grammar, organization, and help students to make revisions. The program scans for key words and analyzes semantic (语义的) patterns, and Pearson claims that it can understand the meaning of text much the same as a human reader.

    Batteries can power anything from small sensors to large systems. While scientists are finding ways to make them smaller but even more powerful, problems can arise when these batteries are much larger and heavier than the devices themselves. University of Missouri (MU) researchers are developing a nuclear energy source that is smaller, lighter and more efficient.

    "To provide enough power, we need certain methods with high energy density (密度)", said Jae Kwon, assistant professor of electrical and computer engineering at MU. ''The radioisotope (放射性同位素) battery can provide power density that is much higher than chemical batteries."

    Kwon and his research team have been working on building a small nuclear battery, presently the size and thickness of a penny, intended to power various micro systems (MNEMS). Although nuclear batteries can cause concerns, Kwon said they are safe.

    "People hear the word 'nuclear' and think of something very dangerous." he said. "However, nuclear power sources have already been safely powering a variety of devices, such as pace-makers, space satellites and underwater systems."

    His new idea is not only in the battery's size, but also in its semiconductor (半导体). Kwon's battery uses a liquid semi conduct or rather than a solid semiconductor.

    "The key part of using a radioactive battery is that when you harvest the energy, part of the radiation energy can damage the lattice structure (晶体结构) of the solid semiconductor." Kwon said, "By using a liquid semiconductor, we believe we can minimize that problem."

    Together with J. David Robertson, chemistry professor and associate director of the MU Research Reactor, Kwon is working to build and test the battery. In the future, they hope to increase the battery's power, shrink its size and try with various other materials. Kwon said that battery could be thinner than the thickness of human hair.

    About one million adults in the USA need someone to help them eat. Researchers at the University of Washington are working on a robotic system that can help make it easier. After identifying different food on a plate, the robot can decide how to use a fork to pick up and deliver the desired bite to a person s mouth.

    "Being dependent on a caregiver to feed every bite every day takes away a person's sense of independence," said the researcher. "Our goal with this project is to give people a bit more control over their lives the idea was to develop a feeding system that would be attached to wheelchairs and feed people whatever they wanted to eat.

    "When we started the project, we realized there are so many ways that people can eat a piece of food depending on its size, shape or consistency(坚实度)," said the researcher, "So we set up an experiment to see how humans eat common foods. "

    The researchers arranged plates with about a dozen different kinds of food, ranging in consistency from hard carrots to soft bananas. Then the team gave volunteers a fork and asked them to pick up different pieces of food and feed them to a model. The fork contained a sensor to measure how much force people used when they picked up food.

    To design a feeding strategy that changes based on the food item, the researchers combined two different algorithms (算法). First they used an object-detection algorithm called Retina Net, which scans the plate, identifies the types of food on it and places a frame around each item. Then they developed SPNet, an algorithm that examines the type of food in a specific frame and tells the robot the best way to pick up the food.

    The team is currently working with the Taskar Center for Accessible Technology to get advice from caregivers and patients on how to improve the system to meet people's need.