1 . Washington, D.C. Bicycle Tours

Cherry Blossom Bike Tour in Washington, D.C.

Duration: 3 hours

This small group bike tour is a fantastic way to see a world-famous cherry trees with beautiful flowers of Washington, D.C. Your guide will provide a history lesson about the trees and the famous monuments where they blossom. Reserve your spot before availability — the cherry blossoms—disappear!

Washington Capital Monuments Bicycle Tour

Duration: 3 hours (4 miles)

Join a guided bike tour and view some of the most popular monuments in Washington, D.C. Explore the monuments and memorials on the National Mall as your guide shares unique facts and history at each stop. Guided tour includes bike, helmet, cookies and bottled water.

Capital City Bike Tour In Washington, D.C.

Duration: 3 hours

Morning or Afternoon, this bike tour is the perfect tour for D. C. newcomers and locals looking to experience Washington, D.C. in a healthy way with minimum effort. Knowledgeable guides will entertain you with the most, interesting stories about Presidents, Congress, memorials, and parks. Comfortable bikes and a smooth tour route(路线) make cycling between the sites fun and relaxing.

Washington Capital Sites at Night Bicycle Tour

Duration: 3 hours (7miles)

Join a small group bike tour for an evening of exploration in the heart of Washington, D.C. Get up close to the monuments and memorials as you bike the sites of Capitol Hill and the National Mall. Frequent stops are made for photo taking as your guide offers unique facts and history. Tour includes bike, helmet, and bottled water. All riders are equipped with reflective vests and safety lights.

2 . We may think we're a culture that gets rid of our worn technology at the first sight of something shiny and new, but a new study shows that we keep using our old devices(装置) well after they go out of style. That’s bad news for the environment — and our wallets — as these outdated devices consume much more energy than the newer ones that do the same things.

To figure out how much power these devices are using, Callie Babbitt and her colleagues at the Rochester Institute of Technology in New York tracked the environmental costs for each product throughout its life — from when its minerals are mined to when we stop using the device. This method provided a readout for how home energy use has evolved since the early 1990s. Devices were grouped by generation — Desktop computers, basic mobile phones, and box-set TVs defined 1992. Digital cameras arrived on the scene in 1997. And MP3 players, smart phones, and LCD TVs entered homes in 2002, before tablets and e-readers showed up in 2007.

As we accumulated more devices, however, we didn't throw out our old ones. "The living-room television is replaced and gets planted in the kids' room, and suddenly one day, you have a TV in every room of the house," said one researcher. The average number of electronic devices rose from four per household in 1992 to 13 in 2007. We're not just keeping these old devices — we continue to use them. According to the analysis of Babbitt's team, old desktop monitors and box TVs with cathode ray tubes are the worst devices with their energy consumption and contribution to greenhouse gas emissions（排放）more than doubling during the 1992 to 2007 window.

So what's the solution（解决方案）? The team's data only went up to 2007, but the researchers also explored what would happen if consumers replaced old products with new electronics that serve more than one function, such as a tablet for word processing and TV viewing. They found that more on-demand entertainment viewing on tablets instead of TVs and desktop computers could cut energy consumption by 44%.

3 . By the end of the century, if not sooner, the world’s oceans will be bluer and greener thanks to a warming climate, according to a new study.

At the heart of the phenomenon lie tiny marine microorganisms(海洋微生物) called phytoplankton. Because of the way light reflects off the organisms, these phytoplankton create colourful patterns at the ocean surface. Ocean colour varies from green to blue, depending on the type and concentration of phytoplankton. Climate change will fuel the growth of phytoplankton in some areas, while reducing it in other spots, leading to changes in the ocean’s appearance.

Phytoplankton live at the ocean surface, where they pull carbon dioxide(二氧化碳) into the ocean while giving off oxygen. When these organisms die, they bury carbon in the deep ocean, an important process that helps to regulate the global climate. But phytoplankton are vulnerable to the ocean’s warming trend. Warming changes key characteristics of the ocean and can affect phytoplankton growth, since they need not only sunlight and carbon dioxide to grow, but also nutrients.

Stephanie Dutkiewicz, a scientist in MIT’s Center for Global Change Science, built a climate model that projects changes to the oceans throughout the century. In a world that warms up by 3℃, it found that multiple changes to the colour of the oceans would occur. The model projects that currently blue areas with little phytoplankton could become even bluer. But in some waters, such as those of the Arctic, a warming will make conditions riper for phytoplankton, and these areas will turn greener. “Not only are the quantities of phytoplankton in the ocean changing. ” she said, “but the type of phytoplankton is changing.”

And why does that matter? Phytoplankton are the base of the food web. If certain kinds begin to disappear from the ocean, Dutkiewicz said, “it will change the type of fish that will be able to survive.” Those kinds of changes could affect the food chain.

Whatever colour changes the ocean experiences in the coming decades will probably be too gradual and unnoticeable, but they could mean significant changes. “It’ll be a while before we can statistically show that the changes are happening because of climate change,” Dutkiewicz said, “but the change in the colour of the ocean will be one of the early warning signals that we really have changed our planet.”

4 . Steven Stein likes to follow garbage trucks. His strange habit makes sense when you consider that he’s an environmental scientist who studies how to reduce litter, including things that fall off garbage trucks as they drive down the road. What is even more interesting is that one of Stein’s jobs is defending an industry behind the plastic shopping bags.

Americans use more than 100 billion thin film plastic bags every year. So many end up in tree branches or along highways that a growing number of cities do not allow them at checkouts(收银台). The bags are prohibited in some 90 cities in California, including Los Angeles. Eyeing these headwinds, plastic-bag makers are hiring scientists like Stein to make the case that their products are not as bad for the planet as most people assume.

Among the bag makers’ argument: many cities with bans still allow shoppers to purchase paper bags, which are easily recycled but require more energy to produce and transport. And while plastic bags may be ugly to look at, they represent a small percentage of all garbage on the ground today.

The industry has also taken aim at the product that has appeared as its replacement: reusable shopping bags. The stronger a reusable bag is, the longer its life and the more plastic-bag use it cancels out. However, longer-lasting reusable bags often require more energy to make. One study found that a cotton bag must be used at least 131 times to be better for the planet than plastic.

Environmentalists don’t dispute(质疑) these points. They hope paper bags will be banned someday too and want shoppers to use the same reusable bags for years.

8 . Million-year-old mammoth genomes push the limits of a revolutionary technique

In the 1966 science-fiction movie “One Million Years B.C. ”, Raquel Welch and John Richardson traverse a primitive landscape inhabited by dinosaurs and early humans. The film was low on science and high on _________: by then dinosaurs were long dead.

A more _________ picture of Earth’s inhabitants at the time is now being revealed. In research published in Nature, a team of scientists led by Anders Gotherstrom and Love Dalen describe sequencing DNA samples from mammoths that lived and died in north-eastern Siberia around a million years ago.

The team’s work represents a new _________, for their mammoth DNA is, by some half a million years, the oldest ever successfully reconstituted. _________ from horses, bears, such ancient DNA has proved an _________ tool for investigating the past. Although fossils preserve the gross physical features of extinct animals, they are _________ about many crucial details that even an incomplete genome can help to fill in.

The trouble with DNA is that it breaks down after death. The more brokendown it is, the _________ it is to sequence. Scientists think that, after about 6m years, all that would be left would be individual base pairs（单个的 碱基对） , the _________ of trying to reconstruct a book from a heap of its constituent letters. Under the right conditions, _________, such as the extreme cold of Arctic permafrost, this decay can be slowed.

Samples were sent to Dr Dalen’s laboratory in 2017 and strands of DNA were extracted, sequenced, and dated. Whereas DNA samples from a living animal can run to several hundreds of thousands of letters, the timeworn mammoth samples __________ strands mere dozens of letters long. This is close to the __________ of what is scientifically usable.

To date a specimen, fragments of its DNA are compared to corresponding chunks from __________ descendants. Analysis of this sort revealed that the youngest molar was between 500,000 and 800,000 years old. A tooth found near the Adycha river was from an animal that had died between 1m and 1.2m years ago. The __________ record had been held by a set of horse DNA thought to be as much as 780,000 years old.

The teeth held other __________. The Krestovka mammoth belongs to a previously unknown branch of the mammoth family tree, an ancestor of the Columbian mammoth which roamed North America 1.5m years ago. The Adycha mammoth was an ancestor of the iconic woolly mammoth. It appeared to possess many of its descendant’s features half a million years earlier, suggesting the woolly mammoth's distinctive physiology evolved more __________ than had been thought.

10 . More than a score of Australian rare mammals have been killed by wild cats. These predators, which arrived with European settlers, still threaten native wildlife — and are too plentiful on the mainland to eliminate, as has been achieved on some small islands which were previously filled with them. But Alexandra Ross of the University of New South Wales thinks she has come up with a different way to deal with the problem. As she writes in a paper in the Journal of Applied Ecology, she is giving feline (猫科的) — awareness lessons to wild animals involved in re-introduction programs, in order to try to make them cat-conscious.

Many Australian mammals, though not actually extinct, are restricted to fragments of cat-free habitat. This will, however, put the forced migrants back in the sights of the cats that caused the problem in the first place. Training the migrants while they are in captivity, using stuffed models and the sorts of sounds made by cats, has proved expensive and ineffective. Ms Ross therefore wondered whether putting them in large natural enclosures with a scattering of predators might serve as a form of training camp to prepare them for introduction into their new, cat-ridden homes.

She tested this idea on a type of bandicoot (袋狸) that superficially resembles a rabbit. She and her colleagues raised two hundred bandicoots in a huge enclosure that also contained five wild cats. As a control, she raised a nearly identical population in a similar enclosure without the cats. She left the animals to get on with life for two years, which, given that bandicoots breed four times a year and live for around eight years, was a considerable period for them. After some predation (扑食) and probably some learning, she abstracted 21 bandicoots from each enclosure, attached radio transmitters to them and released them into a third enclosure that had ten hungry cats in it. She then monitored what happened next. The outcome was that the training worked. Over the subsequent 40 days, ten of the untrained animals were eaten by cats, but only four of the trained ones. One particular behavioral difference she noticed was that bandicoots brought up in a predator-free environment were much more likely to sleep alone than were those brought up around cats. And when cats are around, sleeping alone is dangerous. How well bandicoots that have undergone this extreme training will survive in the wild remains to be seen. But Ms Ross has at least provided reason for hope.