More and more Americans are showing an interest in healthy and locally-produced food. As the interest increases, raising chickens has been gaining popularity in some American cities.

 “Look, we get three eggs this time.”

    Collecting eggs is a daily pleasure for the Hurst family. Naomi Hurst says her family started to raise chickens in back of their home in Maryland a month ago.

   “We have wanted to try having backyard chickens for a couple years now. And really just didn't have the time to build my own coop（鸡笼；鸡舍） and  look out where to buy chickens. And then we met Rent a Coop,” said Naomi Hurst. Rent a Coop is a chicken rental business. Tyler Phillips launched the company with a partner 18 months ago. It comes with a mobile coop on wheels, two egg-laying hens, feed, bedding, water bowl, feed bowl, and our 24-hour chicken hotline. You can call with any questions. The price is 185 dollars for four weeks. After the four weeks passed, individuals can extend the rental agreement, return everything or purchase the animals and supplies.

Tyler Phillips designs and makes the coops. He says he wants to do as little damage as possible to the environment.

 “We always try to have as many recycled materials as possible. And I want the coops to be safe for kids. I want the chickens to be comfortable and they have access to the grass while being inside the coop. I want it to be easily movable, light weight,” he said.

Some cities require people have large pieces of land, if they want to raise farm animals. Others require an agreement with neighbors, limit the number of chickens, or, even ban the birds.

  Tyler Phillips expects that would change as interest in small poultry (家禽) coops grows. 

“I see cities around the D. C. area changing laws almost monthly and different cities will change the law to being prochicken(赞成养鸡). That is happening all around the United States,” he said,

He believes that there will be chicken rental businesses in most American cities within five years.

    EUROPE is home to a variety of cultural treasures. Lonely Planet, the world's largest travel guide publisher, has offered pairs of cities for culture-hungry but time poor travelers.

    London and Paris

    It takes you about two hours to travel from London to Paris by Eurostar, a high-speed railway service. The two capital cities have been competing in fashion, art and nightlife for decades — but each secretly looks up to the other.

    No one can doubt the grand and impressive beauty of Paris' Louvre Museum, but if you want to save money, you cannot skip the British Museum free to visit. Compared with London, Paris has more outdoor attractions, such as the beautiful green walkway La Promenade Plantee.

    In Paris, you'll see diners linger(逗留) over red wine. While in London, you can try some afternoon tea, eat fish and chips or salted cake.

    Vienna and Bratislava

    Austrian capital Vienna and Slovakia city Bratislava are an hour apart by train. But since they are linked by the Danube River, the best way to travel is by ship. A tour of the two cities is the perfect way to experience everything from 17^th century's Habsburg dynast splendor to sci-fi restaurants.

    Vienna is famous for Mozart and imperial palaces. You can appreciate the perfect blending(融合) of architecture and nature in the grand Scholoss Schonbrunn Palace, and reward yourself with a cup of Vienna coffee, which has made its way to the world's cultural heritage.

    Bratislava is best known for its fine dining—the remarkable UFO restaurant. You can enjoy a meat-filled dinner here in an amazing setting.

    Singapore's public transport system is one of the best in the world, so you should have no problem finding your way around like a local. There are three main forms of public transport that you would find in any other major city—trains, buses and taxis.

    TRAINS

    Trains run from 6:00 am to midnight. Single trip tickets start at 80 cents. If you buy an EZ-Link cars for $15, you can ride the trains and buses as you like.

    If you need more information, just call Transit Link on 1800 525 7333.

    BUSES

    There are several bus services in Singapore and fares start at 80 cents. Be sure always ask the driver the cost of your ticket as he can not give change.

    If you need help, just call Transit Link on 1800 525 7333.

    TAXIS

    There are three main taxi companies—City Cab (6552 2222), Comfort (6552 1111) and Tibs (6552 8888). Booking can also be easily by calling the numbers listed above.

    RENTAL CARS

    Driving in Singapore is a pleasure and if you liked to travel at your own pace, renting a car is a good choice. Renting takes away the hassle of getting to places around Singapore. Just sit back and enjoy the city. It also means you'll get to see a lot more that a train or a bus won't let you see.

    For car rental, call Avis on + 65 6737 1668.

    Every summer, my family and I visit our relatives in India and whenever we travel, my parents always remind me to drink only bottled or boiled water. On one of my trips to India, I saw children drinking water from the roadside. I was troubled to learn that millions of people, most of them children in developing countries, die each year because of water related diseases.

    Living in the US, I am lucky to be able to turn on the tap and get potable water(饮用水), while one sixth of the world's population lacks access to clean water This year, I entered the Discovery Education 3M Young Scientist Challenge. In late June, I learned that I was selected as one of the top 10 national finalists of this famous middle school science competition. Over the summer, I worked with Dr. Jim Jonza, my Scientist mentor(导师 )from 3M, and developed a system that uses solar energy to purify water. My invention is green and cost effective, and I am looking forward to implementing this in places that are affected(影响)by harmful water pollution.

    In October, my family and I flew to 3M Headquarters in St Paul, Minnesota, where the final event was to be held. For the last challenge, each of us had to present the invention we had been working on over the summer. The first place winner would win $25,000, a trip to Costa Rica, and the title of America' Top Young Scientist. At the awards ceremony, all of us waited anxiously until one of the judges, Danny Forester, started announcing "The winner of the Discovery Education 3M Young Scientist Challenge is…" You could hear a pin(大头针) drop as he opened the paper with the winner' s name, "Deepika Kurup!"

    As America's Top Young Scientist, I was given an opportunity to show my invention on national television and deliver several presentations. One of the most important things I have learned is that communication and teamwork are key to success.

    The largest genetic study of mosquitoes has found their ability to resist insecticides(杀虫剂) is evolving rapidly and spreading across Africa, putting millions of people at higher risk of contracting malaria(疟疾).

British scientists who led the work said mosquitoes' growing resistance to control tools such as insecticide-treated bed nets and insecticide spraying, which have helped cut malaria cases since 2000, now threatens "to disturb malaria control" in Africa.

    "Our study highlights the severe challenges facing public efforts to control mosquitoes and to manage and limit insecticide resistance," said Martin Donnelly of the Liverpool School of Tropical Medicine, who worked on the study with a team from Britain's Wellcome Trust Sanger Institute.

    Latest World Health Organization (WHO) data show that 216 million people were infected last year with the malaria parasite(寄生虫), which is transmitted by blood-sucking Anopheles mosquitoes. The disease killed 445,000 people in 2016, and the majority of them were children in sub-Saharan Africa.

    To understand how mosquitoes are evolving, the researchers sequenced the DNA of 765 wild Anopheles mosquitoes taken from 15 locations across eight African countries. Their work, published in the journal Nature on Wednesday, created the largest data resource on natural genetic variation for any species of insect.

    Analyzing the data, the scientists found that the Anopheles gamblae mosquitoes(冈比亚疟蚊)were extremely genetically diverse compared with most other animal species. This high genetic diversity enables rapid evolution, they said, and helps to explain how mosquitoes develop insecticide resistance so quickly.

    The data also showed the rapid evolution of insecticide resistance appeared to be due to many previously unknown genetic variants(变体)within certain genes. The scientists said these genetic variants for insecticide resistance were not only emerging independently in different parts of Africa, but were also being spread across the continent by mosquito migration.

    Michael Chew, an expert at Britain's Wellcome Trust global health charity which helped fund the research, said the finds underlined the importance of pushing scientific research ahead to control malaria.

Global efforts to control malaria through effective vaccine, insecticides and the best drug combinations require urgent, united action by scientists, drug companies, governments and the WHO.

    Rivers are earthly arteries(要道) for the nutrients, deposits and freshwater that sustain healthy, diverse ecosystems. Their influence extends in multiple dimensions—not only along their length but below­ground to aquifers(蓄水层) and periodically into nearby floodplains.

    They also provide vital services for people by fertilizing agricultural land and feeding key fisheries and by acting as transportation corridors. But in efforts to ease ship passage, protect communities from flooding, and draw off water for drinking and irrigation, humans have increasingly constrained and broken these crucial water ways. “We try to control rivers as much as possible,” says Gunther Grill, a hydrologist at McGill University.

    In new research published in May in Nature, Grill and his colleagues analyzed the barriers to 12 million total kilometers of rivers around the world. The team developed an index(指数) that evaluates six aspects of connectivity—from physical fragmentation (by dams, for example) to flow regulation (by dams or levees) to water consumption—along a river's various dimension. Rivers whose indexes meet a certain threshold(临界值) for being largely able to follow their natural patterns were considered free­flowing.

    The researchers found that among rivers longer than 1,000 kilometers (which tend to be some of those most important to human activities), only 37 percent are not blocked along their entire lengths. Most of them are in areas with a minimal human presence, including the Amazon and Congo basins and the Arctic. On the contrary, most rivers shorter than 100 kilometers appeared to flow freely—but the data on them are less comprehensive, and some barriers might have been missed. Only 23 percent of the subset of the longest rivers that connect to the ocean are uninterrupted. For the rest, human infrastructure is starving estuaries(河口) and deltas (such as the Mississippi Delta) of key nutrients. The world's estimated 2.8 million dams are the main cause, controlling water flow and trapping deposits.

    The new research could be used to better understand how proposed dams, levees and other such projects might impact river connectivity, as well as where to remove these fixtures to best restore natural flow. It could also help inform our approach to rivers as the climate changes, says Anne Jefferson, a hydrologist at Kent State University, who was not involved in the work. Existing infrastructure, she says, “has essentially been built to a past climate that we are not in anymore and are increasingly moving away from.”