In the frozen continent of Antarctica scientists fear an alien invasion — not from outer space, but carried in people's pockets and bags.

    Seeds and plants accidentally brought to Antarctica by tourists and scientists may introduce alien plant species which could threaten the survival of native plants in the finely balanced ecosystem.

    “The people that were carrying the most had lots and lots of seeds. They really were real threats,” said Dana Bergstrom, from the Australian Antarctic Division.

    “When we take things in through hitchhiking（搭车旅行） then we get species which are competitive. The plants and animals there are not necessarily competitive, so we'd start losing various precious biodiversity（生物多样性） on the (Antarctic) continent”, Bergstrom told Reuters.

    Amongst the alien species discovered were the Iceland Poppy, and Annual Winter Grass — all from cold climates and capable of growing in Antarctica.

    The Antarctic Peninsula, where most tourists travel, is now considered a “hot spot” on the frozen continent and the warmer the climate, the easier for seeds to grow. “The peninsula(半岛) is warming at some of the greatest rates on the planet,” said Bergstrom.

    The study, the first continent-wide assessment of invasive species in Antarctica, surveyed about 1,000 passengers during 2007-2008, the first year of the International Polar Year, an international effort to research the polar areas.

    Bergstrom said the one alien seed that had gained a foothold is Annual Winter Grass. It is a strong weed in the sub-Antarctic and is on the Antarctic island of King George. It has also made its way to the tail part of the Antarctic continent.

    Mom was a teacher most of her life. When she wasn't in the classroom, she was educating her children or grandchildren; correcting our grammar; starting us on collections of butterflies, flowers or rocks; or inspiring a discussion on her most recent “Book of the Month Club” topic. Mom made learning fun.

    It was sad for my three brothers and me to see her suffering in her later years. At eighty- five, she suffered a stroke and she went steadily downhill after that.

    Two days before she died, my brothers and I met at her nursing home and took her for a short ride in a wheelchair. While we waited for the staff to lift her limp body back into bed, Mom fell asleep. Not wanting to wake her, we moved to the far end of the room and spoke softly.

    After several minutes our conversation was interrupted by a muffled sound coming from across the room. We stopped talking and looked at Mom. Her eyes were closed, but she was clearly trying to communicate with us. We went to her side.

    “Whirr,” she said weakly.

    “Where?” I asked. “Mom, is there something you want?” “Whirr,” she repeated a bit stronger. My brothers and I looked at each other and shook our heads sadly.

    Mom opened her eyes, sighed, and with all the energy she could gather said, “Not ...was. Say were!”

    We suddenly realized that Mom was correcting Brother Jim's last sentence. “if it was up to me…”

    Jim leaned down and kissed her cheek. “Thanks, Mom,” he whispered. We smiled at each other and once again shook our heads.

    Researchers have created a backpack that has a computer and medicines in it that can help even untrained soldiers save the lives of wounded troops. Wounded soldiers have a better chance of survival if they get help soon after being hurt and are quickly taken to a hospital or clinic. But soldiers who do not have medical training may not know how to help their injured friends.

    Doctors and engineers have developed what they call an “intelligent backpack”. It has a computer and electronic measuring devices. The backpack also has robotic instruments and medicines ready to give to injured troops.

    About 16 doctors and engineers from the University of Pittsburgh, Carnegie Mellon University and several other places are working on the project. The U. S. Department of Defense has given money to the project.

    Ron Poropatich leads the project. He is a retired army surgeon. He says the backpack will help soldiers care for those who are injured. The devices included in the backpack can monitor a person's heart rate and blood pressure. The robotic instruments can even tell whether the soldier has a collapsed lung.

    The intelligent backpack's computer can compare information gathered about the injured soldier with thousands of similar cases, and quickly tell the best methods to use to save the soldier's life.

    Sometimes, it is not always possible to quickly remove the injured soldier from the battlefield. So, Dr. Poropatich says, the researchers hope to create a backpack that will have devices that can keep a soldier alive for a long time. Dr. Poropatich hopes the backpack and its instruments will be ready for testing animals in about three years.

    You probably know that frogs hop (双足跳). But did you know that there's a small frog in the Pacific Northwest that belly flops (肚子先着水)? It's called a tailed frog.

    Dr. Rick Eisner, who has been studying tailed frogs for the past few years, says, "I've looked at thousands of jumps and have never seen them land on their feet like other frogs." Most of the time, tailed frogs land on their stomachs and then bring their back legs in to prepare for another jump.

    Eisner first noticed these frogs because of the way they swim. Other frogs kick both of their back legs at the same time. But when a tailed frog swims, it pushes first with one leg and then the other.

    To try to find out why tailed frogs bellyflop, Eisner and other scientists collected and filmed different kinds of frogs. They found that all of the frogs start their jumps the same way: They hold out their legs. The change comes in the landing. Tailed frogs can't move their back legs as quickly as other frogs do. Maybe they don't need to. Tailed frogs live around water and quickly jump into the water to escape danger.

    Early frogs developed around watery areas and could jump quickly into the water to escape danger. Scientists think those frogs blended in with (与…融合在一起) the green plants on the side of the rocky rivers, just like today's tailed frogs. "I would guess that other animals would have problems detecting them," explains Eisner. When other animals find those early frogs, the frogs could jump into the river. They didn't need to continue hopping.

    Tailed frogs and other kinds of frogs went their own ways about 200 million years ago. Tailed frogs stayed by rivers. Other kinds of frogs moved to places where new hopping skills allowed them to survive.

    A young woman turns around and around quickly, and jumps high. In the background, a young girl reads a rejection (拒绝) letter from a ballet school. "You have the wrong body for ballet," it says, "and at thirteen, you are too old." This was one of the most popular advertisements (广告) of 2014 and it describes American ballet Theatre's principal (主要的) dancer Misty Copeland.

    This was not a real letter. But Copeland says it is very similar to letters from her childhood. While many dancers start at the age of three. Copeland only began to study ballet in 1995 as a thirteen-year-old.

    People often told her that she was too old, or that she didn't have the perfect body type (She is only 157 cm tall). Her family moved a lot, and it was sometimes difficult for her to attend ballet classes. But Copeland loved dancing and did not want to give up. She stayed with her ballet teacher during the week and spent time with her family only at the weekend. This was a difficult life, but she worked hard and won her first national competition when she was fourteen years old. Copeland joined the American Ballet Theatre in 2000 and performed in many ballets over the next few years. In 2007, she became a solo (单独的) performer, and in 2015 she became its principal dancer.

    Copeland is now a dancer, author and Broadway performer. She also stars in the 2015 film A Ballerina's Tale. So what's next? According to Copeland, anything is possible: "My career (职业) really is just now beginning."

When it comes to lowering blood pressure,studies have typically shown that aerobic(有氧的)exercises are best. Recent research suggests another type of physical activity is worth including as an effective tool to prevent and treat high blood pressure.

Exercises that engage muscles without movement,such as wall squats and planks,may be best for lowering blood pressure,according to a large study published in July,2023 in the British Journal of Sports Medicine.

This type of training is known as isometric exercise,according to the Mayo Clinic.Isometric muscle action happens when muscles contract but do not visibly change length,and the joints involved don't move,facilitating stability of the body.Isometric exercises can be done with weights or without,just relying on the body's own weight.

"These findings provide a comprehensive data-driven framework to support the development of new exercise guideline recommendations for the prevention and treatment of high blood pressure,"said study coauthor Dr.Jamie O'Driscoll in a news release.  The researchers looked into randomized controlled trials that had reported the effects of exercise interventions, lasting two or more weeks,on blood pressure between 1990 and February 2023.From a review of 270 trials with 15,827 participants,the researchers  found that  among HIIT  (high  intensity interval training),isometric  exercise, aerobic exercise,dynamic resistance training and a combination of the latter two,isometric exercise led to the greatest reductions in blood pressure.

It's also important to note that there are other lifestyle changes as well as exercise that can benefit your blood pressure.These include keeping to a healthy weight,eating a balanced diet,cutting down on salt,not drinking too much alcohol and ensuring that you continue to take any prescribed medication.

More research is needed to determine exactly why isometric exercises might be better for lowering blood pressure than other types of training,the authors said.