Questões de Concurso

How things work: 100 scientific explanations

Preservation property has always been important to humans. Historians in the ninth century were the first to record the use of varnish, a protective liquid composed of resins, natural oils, and alcohol, among other ingredients. Furniture makers learned that if they painted coats of the stuff on a piece of furniture or wood floor, it made it impervious to liquids and their damage and shielded it from normal wear and tear. And the makers liked the shine furniture had after it was varnished.

Varnish comes in many formulations. Some are oil based, using linseed or tung oil, while others are water-based. Varnish cures, or dries, on what it’s painted, creating a glossy, clear film on the surface. Some oil-based varnishes can turn to a yellowish color; water-based varieties do not. Wood must be carefully cleaned and sanded before any varnish is applied. Several coats are often required. All varnishes contain resins — terpenes with five-carbon molecules called isoprenes and also include a drying oil or solvent to reduce drying time.

Although furniture and flooors are still the most frequently varnished items, the wooden hulls of boats are also often varnished. Clear nail polish, a type of varnish, can be used for countless small fixes: dab small amounts to keep splintered wood from snagging, prevent ink from running, and stop buttons on clothing or screws on sunglasses from coming loose.

(National Geographic Special Publication “How Things Work” Adapted.)

First study of all Amazon greenhouse gases suggests the

damaged forest is now worsening climate change

The Amazon rainforest is most likely now a net contributor to warming of the planet, according to a first-of-its-kind analysis from more than 30 scientists.

For years, researchers have expressed concern that rising temperatures, drought, and deforestation are reducing the capacity of the world’s largest rainforest to absorb carbon dioxide from the atmosphere, and help offset emissions from fossil-fuel burning. Recent studies have even suggested that some portions of the tropical landscape already may release more carbon than they store.

But the inhaling and exhaling of CO2 is just one way this damp jungle, the most species-rich on Earth, influences the global climate. Activities in the Amazon, both natural and human-caused, can shift the rainforest’s contribution in significant ways, warming the air directly or releasing other greenhouse gases that do.

Yet no team had ever tried to assess the cumulative impact of these processes, even as the region is being rapidly transformed. The research estimates that atmospheric warming from all of these sources combined now appears to swamp the forest’s natural cooling effect.

The damage, however, can still be reversed. Halting global emissions from coal, oil, and natural gas would help restore balance, but curbing Amazon deforestation is a must, along with reducing dam building and increasing efforts to replant trees. Continuing to clear land at current rates appears certain to make warming worse for the entire world.

Internet:<www.nationalgeographic.com> (adapted).

SAINT PATRICK'S DAY

Saint Patrick's Day, also known as The Feast of Saint Patrick, is a traditional holiday celebrated every year on March 17th, the day the patron saint of Ireland, Saint Patrick, died.

Patrick, who was born in the fourth century, lived in the British Isles, a land that had been invaded and conquered first by the Romans and then by Germanic tribes. At the age of 16, Patrick was captured and taken as a slave from the British Isles to what is now Ireland. He lived there for several years herding sheep. He was a religious boy, and he prayed that he would someday return to his homeland.

Legend has it that one night while he was praying, a voice told him to escape from the farm, and find a ship that was waiting for him in a harbor two hundred miles aways. Patrick got to the ship, sailed to Europe, and disembarked in what is now probably France. He ---1--- several of the ship's crew through a dangerous forest, praying all the time. Neither Patrick nor any member of his crew was captured. When some of the men were about to die of starvation, wild animals appeared to them to eat. Events such as these appeared to be miracles and gave rise to later legends surrounding Patrick.

Finally finding his way home, Patrick felt that he was called by God to perform an important mission. He believed it was his duty to go back to Ireland and convert the Celtic people to the Christian Religion.

Patrick arrived in England and became a missionary, traveling from village to village and talking about his faith. Once, several members of a tribe approached Patrick and told him that they found it difficult to understand and believe in the Holy Trinity. Patrick thought a moment, then stooped down and picked one of the plentiful shamrocks growing wild around Ireland. “Here are three leaves", he said, “yet it is one plant. Imagine the Father, Son and the Holy Spirit as each of these leaves. Here they are, yet they are one plant." The tribesmen understood, because Patrick had used a familiar object to explain. From that time on, the shamrock has been a revered symbol of Ireland.

There are lots of stories about Patrick. One of them is about him forcing snakes out of the entire country of Ireland. Even though there are many different stories about how he accomplished such a task, it is probably not true. Patrick died on March 17th, and the Irish people set aside the day to mourn. He became the patron saint of Ireland. Mourning turned to commemorating him and celebrating his life.

Because of Saint Patrick, lots of cities around the world with a large population of Irish have parades. Green is one of the national colors of Ireland. Green stripes are painted on the streets where the parade will travel. People wear green shirts, ties, hair ribbons, and hats. There are even pubs which serve green beer on that day.

Saint Patrick's Day was made an official Christian holiday in the early seventeenth century. It is now observed by the Catholic Church, the Anglican Communion, the Eastern Orthodox Church and Lutheran Church. The day commemorates Saint Patrick and the arrival of Christianity in Ireland. Not only that, but it also celebrates the heritage and culture of the Irish in general.

Source: adapted from http://www.inglesnapontadalingua.com.br/2014/03